30 seconds of code
Curated collection of useful JavaScript snippets
that you can understand in 30 seconds or less.
30 seconds of codeCurated collection of useful JavaScript snippets
that you can understand in 30 seconds or less.
302
snippets
115
contributors
3170
commits
19828
stars
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 many of our snippets are not perfectly suited 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.
Our sophisticated robot helpers pick new snippets from our collection daily, so that you can discover new snippets to enhance your projects:
Filters out all values from an array for which the comparator function does not return true.
Use Array.filter() and Array.findIndex() to find the appropriate values.
const differenceWith = (arr, val, comp) => arr.filter(a => val.findIndex(b => comp(a, b)) === -1); -
differenceWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0], (a, b) => Math.round(a) === Math.round(b)); // [1, 1.2] -
Checks if a string is an anagram of another string (case-insensitive, ignores spaces, punctuation and special characters).
Use String.toLowerCase(), String.replace() with an appropriate regular expression to remove unnecessary characters, String.split(''), Array.sort() and Array.join('') on both strings to normalize them, then check if their normalized forms are equal.
const isAnagram = (str1, str2) => { - const normalize = str => - str - .toLowerCase() - .replace(/[^a-z0-9]/gi, '') - .split('') - .sort() - .join(''); - return normalize(str1) === normalize(str2); -}; -
isAnagram('iceman', 'cinema'); // true -
Replaces all but the last num of characters with the specified mask character.
Use String.slice() to grab the portion of the characters that need to be masked and use String.replace() with a regexp to replace every character with the mask character. Concatenate the masked characters with the remaining unmasked portion of the string. Omit the second argument, num, to keep a default of 4 characters unmasked. If num is negative, the unmasked characters will be at the start of the string. Omit the third argument, mask, to use a default character of '*' for the mask.
const mask = (cc, num = 4, mask = '*') => - ('' + cc).slice(0, -num).replace(/./g, mask) + ('' + cc).slice(-num); -
mask(1234567890); // '******7890' -mask(1234567890, 3); // '*******890' -mask(1234567890, -4, ' -
-
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:
-
- Angelos Chalaris
- 
- Stefan Feješ
- 
- Felix Wu
- 
- atomiks
- 
- King David Martins
- 
- Rohit Tanwar
- 
- Soorena Soleimani
- 
- Robert Mennell
- 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!
-Start by creating a snippet, according to the snippet template. Make sure to follow these simple guidelines:
-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 implemneted function.
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.
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.
- 30 seconds of codeCurated collection of useful JavaScript snippets
that you can understand in 30 seconds or less.
302
snippets
116
contributors
3176
commits
19844
stars
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 many of our snippets are not perfectly suited 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.
Our sophisticated robot helpers pick new snippets from our collection daily, so that you can discover new snippets to enhance your projects:
Creates a pub/sub (publish–subscribe) event hub with emit, on, and off methods.
Use Object.create(null) to create an empty hub object that does not inherit properties from Object.prototype. For emit, resolve the array of handlers based on the event argument and then run each one with Array.forEach() by passing in the data as an argument. For on, create an array for the event if it does not yet exist, then use Array.push() to add the handler to the array. For off, use Array.findIndex() to find the index of the handler in the event array and remove it using Array.splice().
const createEventHub = () => ({ + hub: Object.create(null), + emit(event, data) { + (this.hub[event] || []).forEach(handler => handler(data)); + }, + on(event, handler) { + if (!this.hub[event]) this.hub[event] = []; + this.hub[event].push(handler); + }, + off(event, handler) { + const i = (this.hub[event] || []).findIndex(h => h === handler); + if (i > -1) this.hub[event].splice(i, 1); + } +}); +
const handler = data => console.log(data); +const hub = createEventHub(); +let increment = 0; + +// Subscribe: listen for different types of events +hub.on('message', handler); +hub.on('message', () => console.log('Message event fired')); +hub.on('increment', () => increment++); + +// Publish: emit events to invoke all handlers subscribed to them, passing the data to them as an argument +hub.emit('message', 'hello world'); // logs 'hello world' and 'Message event fired' +hub.emit('message', { hello: 'world' }); // logs the object and 'Message event fired' +hub.emit('increment'); // `increment` variable is now 1 + +// Unsubscribe: stop a specific handler from listening to the 'message' event +hub.off('message', handler); +
Returns a new array with n elements removed from the left.
Use Array.slice() to slice the remove the specified number of elements from the left.
const drop = (arr, n = 1) => arr.slice(n); +
drop([1, 2, 3]); // [2,3] +drop([1, 2, 3], 2); // [3] +drop([1, 2, 3], 42); // [] +
Converts a string to snake case.
Break the string into words and combine them adding _ as a separator, using a regexp.
const toSnakeCase = str => + str && + str + .match(/[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g) + .map(x => x.toLowerCase()) + .join('_'); +
toSnakeCase('camelCase'); // 'camel_case' +toSnakeCase('some text'); // 'some_text' +toSnakeCase('some-mixed_string With spaces_underscores-and-hyphens'); // 'some_mixed_string_with_spaces_underscores_and_hyphens' +toSnakeCase('AllThe-small Things'); // "all_the_smal_things" +toSnakeCase('IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML'); // "i_am_listening_to_fm_while_loading_different_url_on_my_browser_and_also_editing_some_xml_and_html" +
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:
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!
Start by creating a snippet, according to the snippet template. Make sure to follow these simple guidelines:
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 implemneted function.
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.
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.
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:
-
- Angelos Chalaris
-
- Stefan Feješ
-
- Felix Wu
-
- atomiks
-
- King David Martins
-
- Rohit Tanwar
-
- Soorena Soleimani
-
- Robert Mennell
- 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!
-Start by creating a snippet, according to the snippet template. Make sure to follow these simple guidelines:
-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 implemneted function.
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.
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.
-