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
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); +30 seconds of code
Curated collection of useful JavaScript snippets
that you can understand in 30 seconds or less.302
snippets116
contributors3181
commits19847
starsOur 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 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.
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:
byteSize
Returns the length of a string in bytes.
Convert a given string to a
BlobObject and find itssize.const byteSize = str => new Blob([str]).size; +byteSize('😀'); // 4 +byteSize('Hello World'); // 11 +copyToClipboard
⚠️ NOTICE: The same functionality can be easily implemented by using the new asynchronous Clipboard API, which is still experimental but should be used in the future instead of this snippet. Find out more about it here.
Copy a string to the clipboard. Only works as a result of user action (i.e. inside a
clickevent listener).Create a new
<textarea>element, fill it with the supplied data and add it to the HTML document. UseSelection.getRangeAt()to store the selected range (if any). Usedocument.execCommand('copy')to copy to the clipboard. Remove the<textarea>element from the HTML document. Finally, useSelection().addRange()to recover the original selected range (if any).const copyToClipboard = str => { + const el = document.createElement('textarea'); + el.value = str; + el.setAttribute('readonly', ''); + el.style.position = 'absolute'; + el.style.left = '-9999px'; + document.body.appendChild(el); + const selected = + document.getSelection().rangeCount > 0 ? document.getSelection().getRangeAt(0) : false; + el.select(); + document.execCommand('copy'); + document.body.removeChild(el); + if (selected) { + document.getSelection().removeAllRanges(); + document.getSelection().addRange(selected); } -}); -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); -drop
Returns a new array with
nelements 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); // [] -toSnakeCase
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" -Getting started
- If you are new to JavaScript, we suggest you start by taking a look at the Beginner's snippets
- If you want to level up tour JavaScript skills, check out the full Snippet collection
- If you want to see how the project was built and contribute, visit our Github repository
- If you want to check out some more complex snippets, you can visit the Archive
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:
- 30 seconds of CSS by atomiks
- 30 seconds of Python by kriadmin
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!
1Create
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.
2Tag
Run
npm run taggerfrom 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.3Test
You can optionally test your snippet to make our job easier. Simply run
npm run testerto generate the test files for your snippet. Find the related folder for you snippet under the test directory and write some tests. Remember to runnpm run testeragain to make sure your tests are passing.4Pull 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.
\ No newline at end of file +};
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.
