# 30 seconds of code

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

View collection

318
snippets

121
contributors

3493
commits

21258
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:

### isObject

Returns a boolean determining if the passed value is an object or not.

Uses the `Object` constructor to create an object wrapper for the given value. If the value is `null` or `undefined`, create and return an empty object. Οtherwise, return an object of a type that corresponds to the given value.

    const isObject = obj => obj === Object(obj);

Show examples

    isObject([1, 2, 3, 4]); // true
    isObject([]); // true
    isObject(['Hello!']); // true
    isObject({ a: 1 }); // true
    isObject({}); // true
    isObject(true); // false

### JSONToFile

Writes a JSON object to a file.

Use `fs.writeFile()`, template literals and `JSON.stringify()` to write a `json` object to a `.json` file.

    const fs = require('fs');
    const JSONToFile = (obj, filename) =>
      fs.writeFile(`${filename}.json`, JSON.stringify(obj, null, 2));

Show examples

    JSONToFile({ test: 'is passed' }, 'testJsonFile'); // writes the object to 'testJsonFile.json'

### off

Removes an event listener from an element.

Use `EventTarget.removeEventListener()` to remove an event listener from an element. Omit the fourth argument `opts` to use `false` or specify it based on the options used when the event listener was added.

    const off = (el, evt, fn, opts = false) => el.removeEventListener(evt, fn, opts);

Show examples

    const fn = () => console.log('!');
    document.body.addEventListener('click', fn);
    off(document.body, 'click', fn); // no longer logs '!' upon clicking on the page

## 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 your 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 Interviews by fejes713
- 30 seconds of Python by kriadmin

## Top contributors

Angelos Chalaris
Stefan Feješ
Felix Wu
atomiks
King David Martins
Rohit Tanwar
Soorena Soleimani
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 implemneted 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.