diff --git a/docs/index.html b/docs/index.html index e92ddb73f..7fb95d5af 100644 --- a/docs/index.html +++ b/docs/index.html @@ -1,26 +1,34 @@ -30 seconds of code

logo 30 seconds of code

Curated collection of useful JavaScript snippets
that you can understand in 30 seconds or less.

321
snippets

125
contributors

3684
commits

21581
stars

Our philosophy

The core goal of 30 seconds of code is to provide a quality resource for beginner and advanced JavaScript developers alike. We want to help improve the JavaScript ecosystem, by lowering the barrier of entry for newcomers and help seasoned veterans pick up new tricks and remember old ones. In order to achieve this, we have collected hundreds of snippets that can be of use in a wide range of situations. We welcome new contributors and we like fresh ideas, as long as the code is short and easy to grasp in about 30 seconds. The only catch, if you may, is that a few of our snippets are not perfectly optimized for large, enterprise applications and they might not be deemed production-ready.


In order for 30 seconds of code to be as accessible and useful as possible, all of the snippets in the collection are licensed under the CC0-1.0 License, meaning they are absolutely free to use in any project you like. If you like what we do, you can always credit us, but that is not mandatory.


Today's picks

Our sophisticated robot helpers pick new snippets from our collection daily, so that you can discover new snippets to enhance your projects:

elementIsVisibleInViewport

Returns true if the element specified is visible in the viewport, false otherwise.

Use Element.getBoundingClientRect() and the window.inner(Width|Height) values to determine if a given element is visible in the viewport. Omit the second argument to determine if the element is entirely visible, or specify true to determine if it is partially visible.

const elementIsVisibleInViewport = (el, partiallyVisible = false) => {
-  const { top, left, bottom, right } = el.getBoundingClientRect();
-  const { innerHeight, innerWidth } = window;
-  return partiallyVisible
-    ? ((top > 0 && top < innerHeight) || (bottom > 0 && bottom < innerHeight)) &&
-        ((left > 0 && left < innerWidth) || (right > 0 && right < innerWidth))
-    : top >= 0 && left >= 0 && bottom <= innerHeight && right <= innerWidth;
+30 seconds of code
logo 30 seconds of code
Curated collection of useful JavaScript snippets
that you can understand in 30 seconds or less.
321
snippets
125
contributors
3688
commits
21595
stars
Our philosophy
The core goal of 30 seconds of code is to provide a quality resource for beginner and advanced JavaScript developers alike. We want to help improve the JavaScript ecosystem, by lowering the barrier of entry for newcomers and help seasoned veterans pick up new tricks and remember old ones. In order to achieve this, we have collected hundreds of snippets that can be of use in a wide range of situations. We welcome new contributors and we like fresh ideas, as long as the code is short and easy to grasp in about 30 seconds. The only catch, if you may, is that a few of our snippets are not perfectly optimized for large, enterprise applications and they might not be deemed production-ready.

In order for 30 seconds of code to be as accessible and useful as possible, all of the snippets in the collection are licensed under the CC0-1.0 License, meaning they are absolutely free to use in any project you like. If you like what we do, you can always credit us, but that is not mandatory.

Today's picks
Our sophisticated robot helpers pick new snippets from our collection daily, so that you can discover new snippets to enhance your projects:
 
isNumber
Checks if the given argument is a number.
Use typeof to check if a value is classified as a number primitive.
const isNumber = val => typeof val === 'number';
+
isNumber('1'); // false
+isNumber(1); // true
+
onUserInputChange
Run the callback whenever the user input type changes (mouse or touch). Useful for enabling/disabling code depending on the input device. This process is dynamic and works with hybrid devices (e.g. touchscreen laptops).
Use two event listeners. Assume mouse input initially and bind a touchstart event listener to the document. On touchstart, add a mousemove event listener to listen for two consecutive mousemove events firing within 20ms, using performance.now(). Run the callback with the input type as an argument in either of these situations.
const onUserInputChange = callback => {
+  let type = 'mouse',
+    lastTime = 0;
+  const mousemoveHandler = () => {
+    const now = performance.now();
+    if (now - lastTime < 20)
+      (type = 'mouse'), callback(type), document.removeEventListener('mousemove', mousemoveHandler);
+    lastTime = now;
+  };
+  document.addEventListener('touchstart', () => {
+    if (type === 'touch') return;
+    (type = 'touch'), callback(type), document.addEventListener('mousemove', mousemoveHandler);
+  });
 };
-
// 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)
-
mapString
Creates a new string with the results of calling a provided function on every character in the calling string.
Use String.split('') and Array.map() to call the provided function, fn, for each character in str. Use Array.join('') to recombine the array of characters into a string. The callback function, fn, takes three arguments (the current character, the index of the current character and the string mapString was called upon).
const mapString = (str, fn) =>
-  str
-    .split('')
-    .map((c, i) => fn(c, i, str))
-    .join('');
-
mapString('lorem ipsum', c => c.toUpperCase()); // 'LOREM IPSUM'
-
spreadOver
Takes a variadic function and returns a closure that accepts an array of arguments to map to the inputs of the function.
Use closures and the spread operator (...) to map the array of arguments to the inputs of the function.
const spreadOver = fn => argsArr => fn(...argsArr);
-
const arrayMax = spreadOver(Math.max);
-arrayMax([1, 2, 3]); // 3
+
onUserInputChange(type => {
+  console.log('The user is now using', type, 'as an input method.');
+});
+
zip
Creates an array of elements, grouped based on the position in the original arrays.
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.
const zip = (...arrays) => {
+  const maxLength = Math.max(...arrays.map(x => x.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]]
 

Getting started

Related projects
The idea behind 30 seconds of code has inspired some people to create similar collections in other programming languages and environments. Here are the ones we like the most:

Top contributors
chalarangelo Angelos Chalaris
fejes713 Stefan Feješ
flxwu Felix Wu
atomiks atomiks
kingdavidmartins King David Martins
kriadmin Rohit Tanwar
iamsoorena Soorena Soleimani
skatcat31 Robert Mennell
How to contribute
Do you have a cool idea for a new snippet? Maybe some code you use often and is not part of our collection? Contributing to 30 seconds of code is as simple as 1,2,3,4!
1
Create
Start by creating a snippet, according to the snippet template. Make sure to follow these simple guidelines:
  • Your snippet title must be unique and the same as the name of the implemented function.
  • Use the snippet description to explain what your snippet does and how it works.
  • Try to keep the snippet's code short and to the point. Use modern techniques and features.
  • Remember to provide an example of how your snippet works.
  • Your snippet should solve a real-world problem, no matter how simple.
  • Never modify README.md or any of the HTML files.
2
Tag
Run npm run tagger from your terminal, then open the tag_database file and tag your snippet appropriately. Multitagging is also supported, just make sure the first tag you specify is on of the major tags and the one that is most relevant to the implemented function.
3
Test
You can optionally test your snippet to make our job easier. Simply run npm run tester to generate the test files for your snippet. Find the related folder for you snippet under the test directory and write some tests. Remember to run npm run tester again to make sure your tests are passing.
4
Pull request
If you have done everything mentioned above, you should now have an awesome snippet to add to our collection. Simply start a pull request and follow the guidelines provided. Remember to only submit one snippet per pull request, so that we can quickly evaluate and merge your code into the collection.
If you need additional pointers about writing a snippet, be sure to read the complete contribution guidelines.