Merge pull request #2 from Chalarangelo/master

Merge
2017-12-15 11:48:01 +01:00
parent b106585c08 14543a15b6
commit b1d8d9587c
41 changed files with 2284 additions and 909 deletions
--- a/.gitignore
+++ b/.gitignore
@ -1,3 +1,3 @@
 node_modules/
-
 currentSnippet\.js
+*.md.temp.js
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@ -7,7 +7,8 @@ Here's what you can do to help:
 - [Open issues](https://github.com/Chalarangelo/30-seconds-of-code/issues/new) for things you want to see added or modified.
 - Be part of the discussion by helping out with [existing issues](https://github.com/Chalarangelo/30-seconds-of-code/issues) or talking on our [gitter channel](https://gitter.im/30-seconds-of-code/Lobby).
 - Submit [pull requests](https://github.com/Chalarangelo/30-seconds-of-code/pulls) with snippets you have created (see below for guidelines).
- Fix typos in existing snippets or run `npm run lint "snippet-name.md"` on unlinted snippets (yes, this is something we actually want help with).
+- Tag untagged snippets by running `npm run tagger` and adding the appropriate tag next to the script name in `tag_database`.
+- Fix typos in existing snippets or run `npm run linter` to lint unlinted snippets (yes, this is something we actually want help with, as this can take quite a while to run).

 ### Snippet submission and Pull request guidelines

--- a/README.md
+++ b/README.md
--- a/package-lock.json
+++ b/package-lock.json
@ -65,16 +65,6 @@
      "resolved": "https://registry.npmjs.org/ansi-escapes/-/ansi-escapes-1.4.0.tgz",
      "integrity": "sha1-06ioOzGapneTZisT52HHkRQiMG4="
    },
-    "ansi-regex": {
-      "version": "0.2.1",
-      "resolved": "https://registry.npmjs.org/ansi-regex/-/ansi-regex-0.2.1.tgz",
-      "integrity": "sha1-DY6UaWej2BQ/k+JOKYUl/BsiNfk="
-    },
-    "ansi-styles": {
-      "version": "1.1.0",
-      "resolved": "https://registry.npmjs.org/ansi-styles/-/ansi-styles-1.1.0.tgz",
-      "integrity": "sha1-6uy/Zs1waIJ2Cy9GkVgrj1XXp94="
-    },
    "anymatch": {
      "version": "1.3.2",
      "resolved": "https://registry.npmjs.org/anymatch/-/anymatch-1.3.2.tgz",
@ -333,21 +323,39 @@
      "integrity": "sha1-Sm+gc5nCa7pH8LJJa00PtAjFVQ0="
    },
    "chalk": {
-      "version": "0.5.1",
-      "resolved": "https://registry.npmjs.org/chalk/-/chalk-0.5.1.tgz",
-      "integrity": "sha1-Zjs6ZItotV0EaQ1JFnqoN4WPIXQ=",
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/chalk/-/chalk-2.3.0.tgz",
+      "integrity": "sha512-Az5zJR2CBujap2rqXGaJKaPHyJ0IrUimvYNX+ncCy8PJP4ltOGTrHUIo097ZaL2zMeKYpiCdqDvS6zdrTFok3Q==",
+      "dev": true,
      "requires": {
-        "ansi-styles": "1.1.0",
+        "ansi-styles": "3.2.0",
        "escape-string-regexp": "1.0.5",
-        "has-ansi": "0.1.0",
-        "strip-ansi": "0.3.0",
-        "supports-color": "0.2.0"
+        "supports-color": "4.5.0"
      },
      "dependencies": {
+        "ansi-styles": {
+          "version": "3.2.0",
+          "resolved": "https://registry.npmjs.org/ansi-styles/-/ansi-styles-3.2.0.tgz",
+          "integrity": "sha512-NnSOmMEYtVR2JVMIGTzynRkkaxtiq1xnFBcdQD/DnNCYPoEPsVJhM98BDyaoNOQIi7p4okdi3E27eN7GQbsUug==",
+          "dev": true,
+          "requires": {
+            "color-convert": "1.9.1"
+          }
+        },
+        "has-flag": {
+          "version": "2.0.0",
+          "resolved": "https://registry.npmjs.org/has-flag/-/has-flag-2.0.0.tgz",
+          "integrity": "sha1-6CB68cx7MNRGzHC3NLXovhj4jVE=",
+          "dev": true
+        },
        "supports-color": {
-          "version": "0.2.0",
-          "resolved": "https://registry.npmjs.org/supports-color/-/supports-color-0.2.0.tgz",
-          "integrity": "sha1-2S3iaU6z9nMjlz1649i1W0wiGQo="
+          "version": "4.5.0",
+          "resolved": "https://registry.npmjs.org/supports-color/-/supports-color-4.5.0.tgz",
+          "integrity": "sha1-vnoN5ITexcXN34s9WRJQRJEvY1s=",
+          "dev": true,
+          "requires": {
+            "has-flag": "2.0.0"
+          }
        }
      }
    },
@ -442,7 +450,6 @@
      "resolved": "https://registry.npmjs.org/concurrently/-/concurrently-3.5.1.tgz",
      "integrity": "sha512-689HrwGw8Rbk1xtV9C4dY6TPJAvIYZbRbnKSAtfJ7tHqICFGoZ0PCWYjxfmerRyxBG0o3sbG3pe7N8vqPwIHuQ==",
      "requires": {
-        "chalk": "0.5.1",
        "commander": "2.6.0",
        "date-fns": "1.29.0",
        "lodash": "4.17.4",
@ -1346,14 +1353,6 @@
        "function-bind": "1.1.1"
      }
    },
-    "has-ansi": {
-      "version": "0.1.0",
-      "resolved": "https://registry.npmjs.org/has-ansi/-/has-ansi-0.1.0.tgz",
-      "integrity": "sha1-hPJlqujA5qiKEtcCKJS3VoiUxi4=",
-      "requires": {
-        "ansi-regex": "0.2.1"
-      }
-    },
    "has-flag": {
      "version": "1.0.0",
      "resolved": "https://registry.npmjs.org/has-flag/-/has-flag-1.0.0.tgz",
@ -2855,14 +2854,6 @@
        "safe-buffer": "5.1.1"
      }
    },
-    "strip-ansi": {
-      "version": "0.3.0",
-      "resolved": "https://registry.npmjs.org/strip-ansi/-/strip-ansi-0.3.0.tgz",
-      "integrity": "sha1-JfSOoiynkYfzF0pNuHWTR7sSYiA=",
-      "requires": {
-        "ansi-regex": "0.2.1"
-      }
-    },
    "strip-bom": {
      "version": "3.0.0",
      "resolved": "https://registry.npmjs.org/strip-bom/-/strip-bom-3.0.0.tgz",
--- a/package.json
+++ b/package.json
@ -11,10 +11,13 @@
  "description": "A collection of useful Javascript snippets.",
  "version": "1.0.0",
  "main": "index.js",
-  "devDependencies": {},
+  "devDependencies": {
+    "chalk": "^2.3.0"
+  },
  "scripts": {
-    "build-list": "node ./scripts/builder.js",
-    "lint": "node ./scripts/lintSnippet.js",
+    "builder": "node ./scripts/build-script.js",
+    "linter": "node ./scripts/lint-script.js",
+    "tagger": "node ./scripts/tag-script.js",
    "start": "concurrently --kill-others \"nodemon -e js,md -i README.md -x \\\"npm run build-list\\\"\" \"live-server ./build\""
  },
  "repository": {
--- a/scripts/build-script.js
+++ b/scripts/build-script.js
@ -0,0 +1,79 @@
+/*
+  This is the builder script that generates the README file.
+  Run using `npm run builder`.
+*/
+// Load modules
+const fs = require('fs-extra'), path = require('path'), chalk = require('chalk');
+// Set variables for paths
+const snippetsPath = './snippets',  staticPartsPath = './static-parts';
+// Set variables for script
+let snippets = {}, startPart = '', endPart = '', output = '', tagDbData = {};
+// Load helper functions (these are from existing snippets in 30 seconds of code!)
+const objectFromPairs = arr => arr.reduce((a, v) => (a[v[0]] = v[1], a), {});
+const capitalize = (str, lowerRest = false) => str.slice(0, 1).toUpperCase() + (lowerRest ? str.slice(1).toLowerCase() : str.slice(1));
+// Start the timer of the script
+console.time('Builder');
+// Synchronously read all snippets and sort them as necessary (case-insensitive)
+try {
+  let snippetFilenames = fs.readdirSync(snippetsPath);
+  snippetFilenames.sort((a, b) => {
+    a = a.toLowerCase();
+    b = b.toLowerCase();
+    if (a < b) return -1;
+    if (a > b) return 1;
+    return 0;
+  });
+  // Store the data read from each snippet in the appropriate object
+  for(let snippet of snippetFilenames)  snippets[snippet] = fs.readFileSync(path.join(snippetsPath,snippet),'utf8');
+}
+catch (err){  // Handle errors (hopefully not!)
+  console.log(`${chalk.red('ERROR!')} During snippet loading: ${err}`);
+  process.exit(1);
+}
+// Load static parts for the README file
+try {
+  startPart = fs.readFileSync(path.join(staticPartsPath,'README-start.md'),'utf8');
+  endPart = fs.readFileSync(path.join(staticPartsPath,'README-end.md'),'utf8');
+}
+catch (err){ // Handle errors (hopefully not!)
+  console.log(`${chalk.red('ERROR!')} During static part loading: ${err}`);
+  process.exit(1);
+}
+// Load tag data from the database
+try {
+  tagDbData = objectFromPairs(fs.readFileSync('tag_database','utf8').split('\n').slice(0,-1).map(v => v.split(':').slice(0,2)));
+}
+catch (err){  // Handle errors (hopefully not!)
+  console.log(`${chalk.red('ERROR!')} During tag database loading: ${err}`);
+  process.exit(1);
+}
+// Create the output for the README file
+try {
+  // Add the start static part
+  output += `${startPart+'\n'}`;
+  // Loop over tags and snippets to create the table of contents
+  for(let tag of [...new Set(Object.entries(tagDbData).map(t => t[1]))].filter(v => v).sort((a,b) => a.localeCompare(b))){
+    output +=`### ${capitalize(tag, true)}\n`;
+    for(let taggedSnippet of Object.entries(tagDbData).filter(v => v[1] === tag))
+      output += `* [${taggedSnippet[0][0].toUpperCase() + taggedSnippet[0].replace(/-/g,' ').slice(1)}](#${taggedSnippet[0].replace(/\(/g,'').replace(/\)/g,'').toLowerCase()})\n`
+    output += '\n';
+  }
+  // Loop over tags and snippets to create the list of snippets
+  for(let tag of [...new Set(Object.entries(tagDbData).map(t => t[1]))].filter(v => v).sort((a,b) => a.localeCompare(b))){
+    output +=`## ${capitalize(tag, true)}\n`;
+    for(let taggedSnippet of Object.entries(tagDbData).filter(v => v[1] === tag))
+      output += `\n${snippets[taggedSnippet[0]+'.md']+'\n[⬆ back to top](#table-of-contents)\n'}`;
+  }
+  // Add the ending static part
+  output += `\n${endPart+'\n'}`;
+  // Write to the README file
+  fs.writeFileSync('README.md', output);
+}
+catch (err){  // Handle errors (hopefully not!)
+  console.log(`${chalk.red('ERROR!')} During README generation: ${err}`);
+  process.exit(1);
+}
+// Log a success message
+console.log(`${chalk.green('SUCCESS!')} README file generated!`);
+// Log the time taken
+console.timeEnd('Builder');
--- a/scripts/builder.js
+++ b/scripts/builder.js
@ -1,57 +0,0 @@
-var fs = require('fs-extra');
-var path = require('path');
-
-var snippetsPath = './snippets';
-var staticPartsPath = './static-parts';
-
-var snippets = {}, startPart = '', endPart = '', output = '';
-
-console.time('Builder');
-
-try {
-  var snippetFilenames = fs.readdirSync(snippetsPath);
-  snippetFilenames.sort((a, b) => {
-    a = a.toLowerCase();
-    b = b.toLowerCase();
-    if (a < b) {
-      return -1;
-    }
-    if (a > b) {
-      return 1;
-    }
-    return 0;
-  });
-  for(var snippet of snippetFilenames){
-    snippets[snippet] = fs.readFileSync(path.join(snippetsPath,snippet),'utf8');
-  }
-}
-catch (err){
-  console.log('Error during snippet loading: '+err);
-  process.exit(1);
-}
-
-try {
-  startPart = fs.readFileSync(path.join(staticPartsPath,'README-start.md'),'utf8');
-  endPart = fs.readFileSync(path.join(staticPartsPath,'README-end.md'),'utf8');
-}
-catch (err){
-  console.log('Error during static part loading: '+err);
-  process.exit(1);
-}
-
-try {
-  output += `${startPart+'\n'}`;
-  for(var snippet of Object.entries(snippets))
-    output += `* [${snippet[0][0].toUpperCase() + snippet[0].replace(/-/g,' ').slice(1,snippet[0].length-3)}](#${snippet[0].slice(0,snippet[0].length-3).replace(/\(/g,'').replace(/\)/g,'').toLowerCase()})\n`
-  output += '\n';
-  for(var snippet of Object.entries(snippets))
-    output += `${snippet[1]+'\n[⬆ back to top](#table-of-contents)\n'}`;
-  output += `${endPart+'\n'}`;
-  fs.writeFileSync('README.md', output);
-}
-catch (err){
-  console.log('Error during README generation: '+err);
-  process.exit(1);
-}
-
-console.timeEnd('Builder');
--- a/scripts/lint-script.js
+++ b/scripts/lint-script.js
@ -0,0 +1,44 @@
+/*
+  This is the linter script that lints snippets.
+  Run using `npm run linter`.
+*/
+// Load modules
+const fs = require('fs-extra'), cp = require('child_process'), path = require('path'), chalk = require('chalk');
+// Set variables for paths
+var snippetsPath = './snippets';
+// Read files, lint each one individually and update
+try {
+  let snippetFilenames = fs.readdirSync(snippetsPath);
+  snippetFilenames.sort((a, b) => {
+    a = a.toLowerCase();
+    b = b.toLowerCase();
+    if (a < b) return -1;
+    if (a > b) return 1;
+    return 0;
+  });
+  // Read each file, get its code, write it to a temporary file, pass it through
+  // semistandard, get the output from the file, update the original file.
+  for(let snippet of snippetFilenames){
+    // Start a timer for the file
+    console.time(`Linter (${snippet})`);
+    // Synchronously read data from the snippet, get the code, write it to a temporary file
+    let snippetData = fs.readFileSync(path.join(snippetsPath,snippet),'utf8');
+    let originalCode = snippetData.slice(snippetData.indexOf('```js')+5,snippetData.lastIndexOf('```'));
+    fs.writeFileSync(`${snippet}.temp.js`,`${originalCode}`);
+    // Run semistandard asynchronously (only way this manages to run), get linted code
+    // and write back to the original snippet file. Remove temporary file
+    cp.exec(`semistandard "${snippet}.temp.js" --fix`,{},(error, stdOut, stdErr) => {
+      let lintedCode = fs.readFileSync(`${snippet}.temp.js`,'utf8');
+      fs.writeFile(path.join(snippetsPath,snippet), `${snippetData.slice(0, snippetData.indexOf('```js')+5)+lintedCode+'```\n'}`);
+      fs.unlink(`${snippet}.temp.js`);
+      // Log a success message
+      console.log(`${chalk.green('SUCCESS!')} Linted snippet: ${snippet}`);
+      // Log the time taken for the file
+      console.timeEnd(`Linter (${snippet})`);
+    });
+  }
+}
+catch (err){  // Handle errors (hopefully not!)
+  console.log(`${chalk.red('ERROR!')} During linting: ${err}`);
+  process.exit(1);
+}
--- a/scripts/lintSnippet.js
+++ b/scripts/lintSnippet.js
@ -1,31 +0,0 @@
-var fs = require('fs-extra');
-var cp = require('child_process');
-var path = require('path');
-
-var snippetsPath = './snippets';
-var snippetFilename = '';
-
-console.time('Linter');
-
-if(process.argv.length < 3){
-  console.log('Please specify the filename of a snippet to be linted.');
-  console.log('Example usage: npm run lint "snippet-file.md"');
-  process.exit(0);
-}
-else {
-  snippetFilename = process.argv[2];
-  let snippetData = fs.readFileSync(path.join(snippetsPath,snippetFilename),'utf8');
-  try {
-    let originalCode = snippetData.slice(snippetData.indexOf('```js')+5,snippetData.lastIndexOf('```'));
-    fs.writeFileSync('currentSnippet.js',`${originalCode}`);
-    cp.exec('semistandard "currentSnippet.js" --fix',{},(error, stdOut, stdErr) => {
-      let lintedCode = fs.readFileSync('currentSnippet.js','utf8');
-      fs.writeFile(path.join(snippetsPath,snippetFilename), `${snippetData.slice(0, snippetData.indexOf('```js')+5)+lintedCode+'```\n'}`);
-      console.timeEnd('Linter');
-    });
-  }
-  catch (err){
-    console.log('Error during snippet loading: '+err);
-    process.exit(1);
-  }
-}
--- a/scripts/tag-script.js
+++ b/scripts/tag-script.js
@ -0,0 +1,67 @@
+/*
+  This is the tagger script that updates the tag_databse file and logs stats for snippet tags.
+  Run using `npm run tagger`.
+*/
+// Load modules
+const fs = require('fs-extra'), path = require('path'), chalk = require('chalk');
+// Set variables for paths
+const snippetsPath = './snippets';
+// Set variables for script
+let snippets = {}, output = '', tagDbData = {}, missingTags = 0, tagDbStats = {};
+// Load helper functions (these are from existing snippets in 30 seconds of code!)
+const objectFromPairs = arr => arr.reduce((a, v) => (a[v[0]] = v[1], a), {});
+const countOccurrences = (arr, value) => arr.reduce((a, v) => v === value ? a + 1 : a + 0, 0);
+// Start the timer of the script
+console.time('Tagger');
+// Synchronously read all snippets and sort them as necessary (case-insensitive)
+try {
+  let snippetFilenames = fs.readdirSync(snippetsPath);
+  snippetFilenames.sort((a, b) => {
+    a = a.toLowerCase();
+    b = b.toLowerCase();
+    if (a < b) return -1;
+    if (a > b) return 1;
+    return 0;
+  });
+  // Store the data read from each snippet in the appropriate object
+  for(let snippet of snippetFilenames)  snippets[snippet] = fs.readFileSync(path.join(snippetsPath,snippet),'utf8');
+}
+catch (err){ // Handle errors (hopefully not!)
+  console.log(`${chalk.red('ERROR!')} During snippet loading: ${err}`);
+  process.exit(1);
+}
+// Load tag data from the database
+try {
+  tagDbData = objectFromPairs(fs.readFileSync('tag_database','utf8').split('\n').slice(0,-1).map(v => v.split(':').slice(0,2)));
+  tagDbStats = Object.entries(tagDbData).sort((a,b) => a[1].localeCompare(b[1])).reduce((acc, val) => {acc.hasOwnProperty(val[1]) ? acc[val[1]]++ : acc[val[1]] = 1; return acc;}, {});
+}
+catch (err){ // Handle errors (hopefully not!)
+  console.log(`${chalk.red('ERROR!')} During tag database loading: ${err}`);
+  process.exit(1);
+}
+// Update the listing of snippets in tag_database and log the statistics, along with missing scripts
+try {
+  for(let snippet of Object.entries(snippets))
+    if(tagDbData.hasOwnProperty(snippet[0].slice(0,-3)) && tagDbData[snippet[0].slice(0,-3)].trim())
+      output += `${snippet[0].slice(0,-3)}:${tagDbData[snippet[0].slice(0,-3)].trim()}\n`;
+    else {
+      output += `${snippet[0].slice(0,-3)}:\n`;
+      missingTags++;
+      console.log(`${chalk.yellow('Tag missing:')} ${snippet[0].slice(0,-3)}`);
+    }
+  // Write to tag_database
+  fs.writeFileSync('tag_database', output);
+}
+catch (err){  // Handle errors (hopefully not!)
+  console.log(`${chalk.red('ERROR!')} During tag_database generation: ${err}`);
+  process.exit(1);
+}
+// Log statistics for the tag_database file
+console.log(`\n${chalk.bgWhite(chalk.black('=== TAG STATS ==='))}`)
+for(let tagData of Object.entries(tagDbStats).filter(v => v[0] !== 'undefined'))
+  console.log(`${chalk.green(tagData[0])}: ${tagData[1]} snippets`);
+console.log(`${chalk.blue('Untagged snippets:')} ${missingTags}\n`);
+// Log a success message
+console.log(`${chalk.green('SUCCESS!')} tag_database file updated!`);
+// Log the time taken
+console.timeEnd('Tagger');
--- a/snippets/array-concatenation.md
+++ b/snippets/array-concatenation.md
@ -1,6 +1,6 @@
 ### Array concatenation

-Use `Array.concat()` to concatenate and array with any additional arrays and/or values, specified in `args`.
+Use `Array.concat()` to concatenate an array with any additional arrays and/or values, specified in `args`.

 ```js
 const arrayConcat = (arr, ...args) => arr.concat(...args);
--- a/snippets/array-difference.md
+++ b/snippets/array-difference.md
@ -3,6 +3,6 @@
 Create a `Set` from `b`, then use `Array.filter()` on `a` to only keep values not contained in `b`.

 ```js
-const difference = (a, b) => { const s = new Set(b); return a.filter(x => !s.has(x)); }
+const difference = (a, b) => { const s = new Set(b); return a.filter(x => !s.has(x)); };
 // difference([1,2,3], [1,2]) -> [3]
 ```
--- a/snippets/array-intersection.md
+++ b/snippets/array-intersection.md
@ -3,6 +3,6 @@
 Create a `Set` from `b`, then use `Array.filter()` on `a` to only keep values contained in `b`.

 ```js
-const intersection = (a, b) => { const s = new Set(b); return a.filter(x => s.has(x)); }
+const intersection = (a, b) => { const s = new Set(b); return a.filter(x => s.has(x)); };
 // intersection([1,2,3], [4,3,2]) -> [2,3]
 ```
--- a/snippets/array-sample.md
+++ b/snippets/array-sample.md
@ -0,0 +1,9 @@
+### Array sample
+
+Use `Math.random()` to generate a random number, multiply it with `Array.length` and round it of to the nearest whole number using `Math.floor()`. Works with strings too. 
+
+```js
+const sample = arr => arr[Math.floor(Math.random() * arr.length)];
+
+// sample([3, 7, 9, 11]) -> 9 
+```
--- a/snippets/array-union.md
+++ b/snippets/array-union.md
@ -3,6 +3,6 @@
 Create a `Set` with all values of `a` and `b` and convert to an array.

 ```js
-const union = (a, b) => Array.from(new Set([...a, ...b]))
+const union = (a, b) => Array.from(new Set([...a, ...b]));
 // union([1,2,3], [4,3,2]) -> [1,2,3,4]
 ```
--- a/snippets/array-zip.md
+++ b/snippets/array-zip.md
@ -0,0 +1,17 @@
+### Array zip
+
+Use `Math.max.apply` to get the longest array in the arguments.
+Creates an array with that length as return value and use `Array.from` with a map-function to create an array of grouped elements.
+If lengths of the argument-arrays vary, `undefined` is used where no value could be found.
+
+```js
+const zip = (...arrays) => {
+  const maxLength = Math.max.apply(null, arrays.map(a => a.length));
+  return Array.from({length: maxLength}).map((_, i) => {
+   return Array.from({length: arrays.length}, (_, k) => arrays[k][i])
+  })
+}
+
+//zip(['a', 'b'], [1, 2], [true, false]); -> [['a', 1, true], ['b', 2, false]]
+//zip(['a'], [1, 2], [true, false]); -> [['a', 1, true], [undefined, 2, false]]
+```
--- a/snippets/chunk-array.md
+++ b/snippets/chunk-array.md
@ -7,5 +7,5 @@ If the original array can't be split evenly, the final chunk will contain the re
 ```js
 const chunk = (arr, size) =>
  Array.from({length: Math.ceil(arr.length / size)}, (v, i) => arr.slice(i * size, i * size + size));
-// chunk([1,2,3,4,5], 2) -> [[1,2],[3,4],5]
+// chunk([1,2,3,4,5], 2) -> [[1,2],[3,4],[5]]
 ```
--- a/snippets/collatz-algorithm.md
+++ b/snippets/collatz-algorithm.md
@ -3,7 +3,7 @@
 If `n` is even, return `n/2`. Otherwise  return `3n+1`.

 ```js
-const collatz = n => (n % 2 == 0) ? (n/2) : (3*n+1); 
+const collatz = n => (n % 2 == 0) ? (n / 2) : (3 * n + 1);
 // collatz(8) --> 4
 // collatz(5) --> 16
 ```
--- a/snippets/curry.md
+++ b/snippets/curry.md
@ -6,13 +6,10 @@ Otherwise return a curried function `f` that expects the rest of the arguments.
 If you want to curry a function that accepts a variable number of arguments (a variadic function, e.g. `Math.min()`), you can optionally pass the number of arguments to the second parameter `arity`.

 ```js
-const curry = (f, arity = f.length, next) =>
-  (next = prevArgs =>
-    nextArg => {
-      const args = [ ...prevArgs, nextArg ];
-      return args.length >= arity ? f(...args) : next(args);
-    }
-  )([]);
+const curry = (fn, arity = fn.length, ...args) =>
+  arity <= args.length
+    ? fn(...args)
+    : curry.bind(null, fn, arity, ...args);
 // curry(Math.pow)(2)(10) -> 1024
 // curry(Math.min, 3)(10)(50)(2) -> 2
 ```
--- a/snippets/deep-flatten-array.md
+++ b/snippets/deep-flatten-array.md
@ -1,10 +1,9 @@
 ### Deep flatten array

 Use recursion.
-Use `Array.reduce()` to get all elements that are not arrays, flatten each element that is an array.
+Use `[].concat()` and the spread operator `...` to flatten an array, and recursively flatten each element that is an array.

 ```js
-const deepFlatten = arr =>
-  arr.reduce((a, v) => a.concat(Array.isArray(v) ? deepFlatten(v) : v), []);
+const deepFlatten = arr => [].concat(...arr.map(v => Array.isArray(v) ? deepFlatten(v) : v));
 // deepFlatten([1,[2],[[3],4],5]) -> [1,2,3,4,5]
 ```
--- a/snippets/drop-elements-in-array.md
+++ b/snippets/drop-elements-in-array.md
@ -4,9 +4,9 @@ Loop through the array, using `Array.shift()` to drop the first element of the a
 Returns the remaining elements.

 ```js
-const dropElements = (arr,func) => {
-  while(arr.length > 0 && !func(arr[0])) arr.shift();
+const dropElements = (arr, func) => {
+  while (arr.length > 0 && !func(arr[0])) arr.shift();
  return arr;
-}
+};
 // dropElements([1, 2, 3, 4], n => n >= 3) -> [3,4]
 ```
--- a/snippets/element-is-visible-in-viewport.md
+++ b/snippets/element-is-visible-in-viewport.md
@ -12,7 +12,7 @@ const elementIsVisibleInViewport = (el, partiallyVisible = false) => {
    ? ((top > 0 && top < innerHeight) || (bottom > 0 && bottom < innerHeight)) &&
      ((left > 0 && left < innerWidth) || (right > 0 && right < innerWidth))
    : top >= 0 && left >= 0 && bottom <= innerHeight && right <= innerWidth;
-}
+};
 // e.g. 100x100 viewport and a 10x10px element at position {top: -1, left: 0, bottom: 9, right: 10}
 // elementIsVisibleInViewport(el) -> false (not fully visible)
 // elementIsVisibleInViewport(el, true) -> true (partially visible)
--- a/snippets/fill-array.md
+++ b/snippets/fill-array.md
@ -4,7 +4,7 @@ Use `Array.map()` to map values between `start` (inclusive) and `end` (exclusive
 Omit `start` to start at the first element and/or `end` to finish at the last.

 ```js
-const fillArray = (arr, value, start = 0, end = arr.length) => 
-  arr.map((v,i) => i>=start && i<end ? value : v);
+const fillArray = (arr, value, start = 0, end = arr.length) =>
+  arr.map((v, i) => i >= start && i < end ? value : v);
 // fillArray([1,2,3,4],'8',1,3) -> [1,'8','8',4]
 ```
--- a/snippets/flatten-array-up-to-depth.md
+++ b/snippets/flatten-array-up-to-depth.md
@ -7,7 +7,7 @@ Omit the second element, `depth` to flatten only to a depth of `1` (single flatt

 ```js
 const flattenDepth = (arr, depth = 1) =>
-  depth != 1 ? arr.reduce((a, v) => a.concat(Array.isArray(v) ? flattenDepth (v, depth-1) : v), []) 
-  : arr.reduce((a,v) => a.concat(v),[]);
+  depth != 1 ? arr.reduce((a, v) => a.concat(Array.isArray(v) ? flattenDepth(v, depth - 1) : v), [])
+  : arr.reduce((a, v) => a.concat(v), []);
 // flattenDepth([1,[2],[[[3],4],5]], 2) -> [1,2,[3],4,5]
 ```
--- a/snippets/get-days-difference-between-dates.md
+++ b/snippets/get-days-difference-between-dates.md
@ -0,0 +1,8 @@
+### Get days difference between dates
+
+Calculate the difference (in days) between to `Date` objects.
+
+```js
+const getDaysDiffBetweenDates = (dateInitial, dateFinal) => (dateFinal - dateInitial) / (1000 * 3600 * 24);
+// getDaysDiffBetweenDates(new Date("2017-12-13"), new Date("2017-12-22")) -> 9
+```
--- a/snippets/is-array.md
+++ b/snippets/is-array.md
@ -3,7 +3,7 @@
 Use `Array.isArray()` to check if a value is classified as an array.

 ```js
-const isArray = val => val && Array.isArray(val);
+const isArray = val => !!val && Array.isArray(val);
 // isArray(null) -> false
 // isArray([1]) -> true
 ```
--- a/snippets/measure-time-taken-by-function.md
+++ b/snippets/measure-time-taken-by-function.md
@ -1,13 +1,14 @@
 ### Measure time taken by function

-Use `performance.now()` to get start and end time for the function, `console.log()` the time taken.
-Pass a callback function as the argument.
+Use `console.time()` and `console.timeEnd()` to measure the difference between the start and end times to determine how long the callback took to execute.

 ```js
 const timeTaken = callback => {
-  const t0 = performance.now(), r = callback();
-  console.log(performance.now() - t0);
+  console.time('timeTaken');
+  const r = callback();
+  console.timeEnd('timeTaken');
  return r;
 };
-// timeTaken(() => Math.pow(2, 10)) -> 1024 (0.010000000009313226 logged in console)
+// timeTaken(() => Math.pow(2, 10)) -> 1024
+// (logged): timeTaken: 0.02099609375ms
 ```
--- a/snippets/nth-element-of-array.md
+++ b/snippets/nth-element-of-array.md
@ -0,0 +1,11 @@
+### Nth element of array
+
+Use `Array.slice()` to get an array containing the nth element at the first place. 
+If the index is out of bounds, return `[]`.
+Omit the second argument, `n`, to get the first element of the array.
+
+```js
+const nth = (arr, n=0) => (n>0? arr.slice(n,n+1) : arr.slice(n))[0];
+// nth(['a','b','c'],1) -> 'b'
+// nth(['a','b','b']-2) -> 'a'
+```
--- a/snippets/number-to-array-of-digits.md
+++ b/snippets/number-to-array-of-digits.md
@ -0,0 +1,9 @@
+### Number to array of digits
+
+Convert the number to a string, use `split()` to convert build an array.
+Use `Array.map()` and `parseInt()` to transform each value to an integer. 
+
+```js
+const digitize = n => (''+n).split('').map(i => parseInt(i));
+// digitize(2334) -> [2, 3, 3, 4]
+```
--- a/snippets/ordinal-suffix-of-number.md
+++ b/snippets/ordinal-suffix-of-number.md
@ -7,9 +7,9 @@ If digit is found in teens pattern, use teens ordinal.
 ```js
 const toOrdinalSuffix = num => {
  const int = parseInt(num), digits = [(int % 10), (int % 100)],
-    ordinals = ["st", "nd", "rd", "th"], oPattern = [1,2,3,4],
-    tPattern = [11, 12, 13, 14, 15, 16, 17, 18, 19]
-  return oPattern.includes(digits[0]) && !tPattern.includes(digits[1]) ? int + ordinals[digits[0]-1] : int + ordinals[3];
-}
+    ordinals = ['st', 'nd', 'rd', 'th'], oPattern = [1, 2, 3, 4],
+    tPattern = [11, 12, 13, 14, 15, 16, 17, 18, 19];
+  return oPattern.includes(digits[0]) && !tPattern.includes(digits[1]) ? int + ordinals[digits[0] - 1] : int + ordinals[3];
+};
 // toOrdinalSuffix("123") -> "123rd"
 ```
--- a/snippets/pipe.md
+++ b/snippets/pipe.md
@ -1,8 +1,15 @@
 ### Pipe

-Use `Array.reduce()` to pass value through functions.
+Use `Array.reduce()` to perform left-to-right function composition. The first (leftmost) function can accept one or more arguments; the remaining functions must be unary. 

 ```js
-const pipe = (...funcs) => arg => funcs.reduce((acc, func) => func(acc), arg);
-// pipe(btoa, x => x.toUpperCase())("Test") -> "VGVZDA=="
+const pipe = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args)))
+/*
+const add5 = x => x + 5
+const multiply = (x, y) => x * y 
+
+const multiplyAndAdd5 = pipe(multiply, add5)
+
+multiplyAndAdd5(5, 2) -> 15
+*/
 ```
--- a/snippets/redirect-to-URL.md
+++ b/snippets/redirect-to-URL.md
--- a/snippets/round-number-to-n-digits.md
+++ b/snippets/round-number-to-n-digits.md
@ -0,0 +1,9 @@
+### Round number to n digits
+
+Use `Math.round()` and template literals to round the number to the specified number of digits.
+Omit the second argument, `decimals` to round to an integer.
+
+```js
+const round = (n, decimals=0) => Number(`${Math.round(`${n}e${decimals}`)}e-${decimals}`);
+// round(1.005, 2) -> 1.01
+```
--- a/snippets/shallow-clone-object.md
+++ b/snippets/shallow-clone-object.md
@ -0,0 +1,12 @@
+### Shallow clone object
+
+Use the object `...spread` operator to spread the properties of the target object into the clone.
+
+```js
+const shallowClone = obj => ({ ...obj });
+/*
+const a = { x: true, y: 1 };
+const b = shallowClone(a);
+a === b -> false
+*/
+```
--- a/snippets/speech-synthesis-(experimental).md
+++ b/snippets/speech-synthesis-(experimental).md
@ -0,0 +1,15 @@
+### Speech synthesis (experimental)
+
+Use `SpeechSynthesisUtterance.voice` and `indow.speechSynthesis.getVoices()` to convert a message to speech.
+Use `window.speechSynthesis.speak()` to play the message.
+
+Learn more about the [SpeechSynthesisUtterance interface of the Web Speech API](https://developer.mozilla.org/en-US/docs/Web/API/SpeechSynthesisUtterance).
+
+```js
+const speak = message => {
+  const msg = new SpeechSynthesisUtterance(message);
+  msg.voice = window.speechSynthesis.getVoices()[0];
+  window.speechSynthesis.speak(msg);
+};
+// speak('Hello, World') -> plays the message
+```
--- a/snippets/standard-deviation.md
+++ b/snippets/standard-deviation.md
@ -11,7 +11,7 @@ const standardDeviation = (arr, usePopulation = false) => {
    arr.reduce((acc, val) => acc.concat(Math.pow(val - mean, 2)), [])
       .reduce((acc, val) => acc + val, 0) / (arr.length - (usePopulation ? 0 : 1))
  );
- }
+};
 // standardDeviation([10,2,38,23,38,23,21]) -> 13.284434142114991 (sample)
 // standardDeviation([10,2,38,23,38,23,21], true) -> 12.29899614287479 (population)
 ```
--- a/snippets/take.md
+++ b/snippets/take.md
@ -4,7 +4,6 @@ Use `Array.slice()` to create a slice of the array with `n` elements taken from

 ```js
 const take = (arr, n = 1) => arr.slice(0, n);
-
 // take([1, 2, 3], 5) -> [1, 2, 3]
 // take([1, 2, 3], 0) -> []
 ```
--- a/snippets/takeRight.md
+++ b/snippets/takeRight.md
@ -0,0 +1,10 @@
+### takeRight
+
+Use `Array.slice()` to create a slice of the array with `n` elements taken from the end.
+
+```js
+const takeRight = (arr, n = 1) => arr.slice(arr.length - n, arr.length);
+// takeRight([1, 2, 3], 2) -> [ 2, 3 ]
+// takeRight([1, 2, 3]) -> [3]
+// takeRight([1, 2, 3]) -> []
+```
--- a/snippets/without.md
+++ b/snippets/without.md
@ -0,0 +1,12 @@
+### Without
+
+Use `Array.filter()` to create an array excluding all given values
+
+```js
+
+const without = (arr, ...args) => arr.filter(v => args.indexOf(v) === -1)
+
+// without[2, 1, 2, 3], 1, 2) -> [3]
+// without([2, 1, 2, 3, 4, 5, 5, 5, 3, 2, 7, 7], 3, 1, 5, 2) -> [ 4, 7, 7 ]
+
+```
--- a/89
+++ b/89
@ -0,0 +1,89 @@
+anagrams-of-string-(with-duplicates):string
+array-concatenation:array
+array-difference:array
+array-intersection:array
+array-union:array
+average-of-array-of-numbers:array
+bottom-visible:browser
+capitalize-first-letter-of-every-word:string
+capitalize-first-letter:string
+chain-asynchronous-functions:function
+check-for-palindrome:string
+chunk-array:array
+collatz-algorithm:math
+compact:array
+count-occurrences-of-a-value-in-array:array
+current-URL:browser
+curry:function
+deep-flatten-array:array
+distance-between-two-points:math
+divisible-by-number:math
+drop-elements-in-array:array
+element-is-visible-in-viewport:browser
+escape-regular-expression:utility
+even-or-odd-number:math
+factorial:math
+fibonacci-array-generator:math
+fill-array:array
+filter-out-non-unique-values-in-an-array:array
+flatten-array-up-to-depth:array
+flatten-array:array
+get-days-difference-between-dates:date
+get-max-value-from-array:array
+get-min-value-from-array:array
+get-native-type-of-value:utility
+get-scroll-position:browser
+greatest-common-divisor-(GCD):math
+group-by:array
+hamming-distance:math
+head-of-list:array
+initial-of-list:array
+initialize-array-with-range:array
+initialize-array-with-values:array
+is-array:utility
+is-boolean:utility
+is-function:utility
+is-number:utility
+is-string:utility
+is-symbol:utility
+last-of-list:array
+measure-time-taken-by-function:utility
+median-of-array-of-numbers:array
+nth-element-of-array:array
+number-to-array-of-digits:utility
+object-from-key-value-pairs:object
+object-to-key-value-pairs:object
+ordinal-suffix-of-number:utility
+percentile:math
+pick:array
+pipe:function
+powerset:math
+promisify:function
+random-integer-in-range:utility
+random-number-in-range:utility
+redirect-to-URL:browser
+reverse-a-string:string
+RGB-to-hexadecimal:utility
+round-number-to-n-digits:math
+run-promises-in-series:function
+scroll-to-top:browser
+shallow-clone-object:object
+shuffle-array:array
+similarity-between-arrays:array
+sleep:function
+sort-characters-in-string-(alphabetical):string
+speech-synthesis-(experimental):media
+standard-deviation:math
+sum-of-array-of-numbers:array
+swap-values-of-two-variables:utility
+tail-of-list:array
+take:array
+takeRight:array
+truncate-a-string:string
+unique-values-of-array:array
+URL-parameters:utility
+UUID-generator:utility
+validate-email:utility
+validate-number:utility
+value-or-default:utility
+without:array
--- a/yarn.lock
+++ b/yarn.lock