The JavaScript Cookbook

Note: this is a living document. Over time this post will fill up with tons of useful how-tos

Strings

• How to uppercase the first letter of a string in JavaScript
• How to check if a string contains a substring in JavaScript
• How to replace all occurrences of a string in JavaScript
• How to convert a string to a number in JavaScript
• How to create a multiline string in JavaScript
• How to check if a string starts with another in JavaScript

Numbers

• How to trim the leading zero in a number in JavaScript
• How to format a number as a currency value in JavaScript
• How to generate a random number between two numbers in JavaScript

Dates

• How to get the current timestamp in JavaScript

Objects

• How to remove a property from a JavaScript object
• How to inspect a JavaScript object
• How to deep clone a JavaScript object
• How to check if a JavaScript object property is undefined
• How to merge two objects in JavaScript
• How to access a method of an object dynamically in JavaScript
• How to use the destructuring syntax to work with arrays and objects in JavaScript
• How to count the number of properties in a JavaScript object
• How to list all methods of an object in JavaScript

Arrays

• How to remove an item from an Array in JavaScript
• How to append an item to an array in JavaScript
• How to initialize a new array with values in JavaScript
• How to use Async and Await with Array.map()
• How to empty a JavaScript array
• How to sort an array of objects by a property value in JavaScript
• How to get the unique properties of a set of objects in a JavaScript array

Functions

• How to set default parameter values in JavaScript

Loops

• How to get the index of an iteration in a for-of loop in JavaScript

More js tutorials:

• Things to avoid in JavaScript (the bad parts)
• Deferreds and Promises in JavaScript (+ Ember.js example)
• How to upload files to the server using JavaScript
• JavaScript Coding Style
• An introduction to JavaScript Arrays
• Introduction to the JavaScript Programming Language
• The Complete ECMAScript 2015-2019 Guide
• Understanding JavaScript Promises
• The Lexical Structure of JavaScript
• JavaScript Types
• JavaScript Variables
• A list of sample Web App Ideas
• An introduction to Functional Programming with JavaScript
• Modern Asynchronous JavaScript with Async and Await
• JavaScript Loops and Scope
• The Map JavaScript Data Structure
• The Set JavaScript Data Structure
• A guide to JavaScript Template Literals
• Roadmap to Learn JavaScript
• JavaScript Expressions
• Discover JavaScript Timers
• JavaScript Events Explained
• JavaScript Loops
• Write JavaScript loops using map, filter, reduce and find
• The JavaScript Event Loop
• JavaScript Functions
• The JavaScript Glossary
• JavaScript Closures explained
• A tutorial to JavaScript Arrow Functions
• A guide to JavaScript Regular Expressions
• How to check if a string contains a substring in JavaScript
• How to remove an item from an Array in JavaScript
• How to deep clone a JavaScript object
• Introduction to Unicode and UTF-8
• Unicode in JavaScript
• How to uppercase the first letter of a string in JavaScript
• How to format a number as a currency value in JavaScript
• How to convert a string to a number in JavaScript
• this in JavaScript
• How to get the current timestamp in JavaScript
• JavaScript Strict Mode
• JavaScript Immediately-invoked Function Expressions (IIFE)
• How to redirect to another web page using JavaScript
• How to remove a property from a JavaScript object
• How to append an item to an array in JavaScript
• How to check if a JavaScript object property is undefined
• Introduction to ES Modules
• Introduction to CommonJS
• JavaScript Asynchronous Programming and Callbacks
• How to replace all occurrences of a string in JavaScript
• A quick reference guide to Modern JavaScript Syntax
• How to trim the leading zero in a number in JavaScript
• How to inspect a JavaScript object
• The definitive guide to JavaScript Dates
• A Moment.js tutorial
• Semicolons in JavaScript
• The JavaScript Arithmetic operators
• The JavaScript Math object
• Generate random and unique strings in JavaScript
• How to make your JavaScript functions sleep
• JavaScript Prototypal Inheritance
• JavaScript Exceptions
• How to use JavaScript Classes
• The JavaScript Cookbook
• Quotes in JavaScript
• How to validate an email address in JavaScript
• How to get the unique properties of a set of objects in a JavaScript array
• How to check if a string starts with another in JavaScript
• How to create a multiline string in JavaScript
• The ES6 Guide
• How to get the current URL in JavaScript
• The ES2016 Guide
• How to initialize a new array with values in JavaScript
• The ES2017 Guide
• The ES2018 Guide
• How to use Async and Await with Array.prototype.map()
• Async vs sync code
• How to generate a random number between two numbers in JavaScript
• HTML Canvas API Tutorial
• How to get the index of an iteration in a for-of loop in JavaScript
• What is a Single Page Application?
• An introduction to WebAssembly
• Introduction to JSON
• The JSONP Guide
• Should you use or learn jQuery in 2020?
• How to hide a DOM element using plain JavaScript
• How to merge two objects in JavaScript
• How to empty a JavaScript array
• How to encode a URL with JavaScript
• How to set default parameter values in JavaScript
• How to sort an array of objects by a property value in JavaScript
• How to count the number of properties in a JavaScript object
• call() and apply() in JavaScript
• Introduction to PeerJS, the WebRTC library
• Work with objects and arrays using Rest and Spread
• Destructuring Objects and Arrays in JavaScript
• The definitive guide to debugging JavaScript
• The TypeScript Guide
• Dynamically select a method of an object in JavaScript
• Passing undefined to JavaScript Immediately-invoked Function Expressions
• Loosely typed vs strongly typed languages
• How to style DOM elements using JavaScript
• Casting in JavaScript
• JavaScript Generators Tutorial
• The node_modules folder size is not a problem. It's a privilege
• How to solve the unexpected identifier error when importing modules in JavaScript
• How to list all methods of an object in JavaScript
• The String replace() method
• The String search() method
• How I run little JavaScript snippets
• The ES2019 Guide
• The String charAt() method
• The String charCodeAt() method
• The String codePointAt() method
• The String concat() method
• The String endsWith() method
• The String includes() method
• The String indexOf() method
• The String lastIndexOf() method
• The String localeCompare() method
• The String match() method
• The String normalize() method
• The String padEnd() method
• The String padStart() method
• The String repeat() method
• The String slice() method
• The String split() method
• The String startsWith() method
• The String substring() method
• The String toLocaleLowerCase() method
• The String toLocaleUpperCase() method
• The String toLowerCase() method
• The String toString() method
• The String toUpperCase() method
• The String trim() method
• The String trimEnd() method
• The String trimStart() method
• Memoization in JavaScript
• The String valueOf() method
• JavaScript Reference: String
• The Number isInteger() method
• The Number isNaN() method
• The Number isSafeInteger() method
• The Number parseFloat() method
• The Number parseInt() method
• The Number toString() method
• The Number valueOf() method
• The Number toPrecision() method
• The Number toExponential() method
• The Number toLocaleString() method
• The Number toFixed() method
• The Number isFinite() method
• JavaScript Reference: Number
• JavaScript Property Descriptors
• The Object assign() method
• The Object create() method
• The Object defineProperties() method
• The Object defineProperty() method
• The Object entries() method
• The Object freeze() method
• The Object getOwnPropertyDescriptor() method
• The Object getOwnPropertyDescriptors() method
• The Object getOwnPropertyNames() method
• The Object getOwnPropertySymbols() method
• The Object getPrototypeOf() method
• The Object is() method
• The Object isExtensible() method
• The Object isFrozen() method
• The Object isSealed() method
• The Object keys() method
• The Object preventExtensions() method
• The Object seal() method
• The Object setPrototypeOf() method
• The Object values() method
• The Object hasOwnProperty() method
• The Object isPrototypeOf() method
• The Object propertyIsEnumerable() method
• The Object toLocaleString() method
• The Object toString() method
• The Object valueOf() method
• JavaScript Reference: Object
• JavaScript Assignment Operator
• JavaScript Internationalization
• JavaScript typeof Operator
• JavaScript new Operator
• JavaScript Comparison Operators
• JavaScript Operators Precedence Rules
• JavaScript instanceof Operator
• JavaScript Statements
• JavaScript Scope
• JavaScript Type Conversions (casting)
• JavaScript Equality Operators
• The JavaScript if/else conditional
• The JavaScript Switch Conditional
• The JavaScript delete Operator
• JavaScript Function Parameters
• The JavaScript Spread Operator
• JavaScript Return Values
• JavaScript Logical Operators
• JavaScript Ternary Operator
• JavaScript Recursion
• JavaScript Object Properties
• JavaScript Error Objects
• The JavaScript Global Object
• The JavaScript filter() Function
• The JavaScript map() Function
• The JavaScript reduce() Function
• The JavaScript `in` operator
• JavaScript Operators
• How to get the value of a CSS property in JavaScript
• How to add an event listener to multiple elements in JavaScript
• JavaScript Private Class Fields
• How to sort an array by date value in JavaScript
• JavaScript Public Class Fields
• JavaScript Symbols
• How to use the JavaScript bcrypt library
• How to rename fields when using object destructuring
• How to check types in JavaScript without using TypeScript
• How to check if a JavaScript array contains a specific value
• What does the double negation operator !! do in JavaScript?
• Which equal operator should be used in JavaScript comparisons? == vs ===
• Is JavaScript still worth learning?
• How to return the result of an asynchronous function in JavaScript
• How to check if an object is empty in JavaScript
• How to break out of a for loop in JavaScript
• How to add item to an array at a specific index in JavaScript
• Why you should not modify a JavaScript object prototype
• What's the difference between using let and var in JavaScript?
• Links used to activate JavaScript functions
• How to join two strings in JavaScript
• How to join two arrays in JavaScript
• How to check if a JavaScript value is an array?
• How to get last element of an array in JavaScript?
• How to send urlencoded data using Axios
• How to get tomorrow's date using JavaScript
• How to get yesterday's date using JavaScript
• How to get the month name from a JavaScript date
• How to check if two dates are the same day in JavaScript
• How to check if a date refers to a day in the past in JavaScript
• JavaScript labeled statements
• How to wait for 2 or more promises to resolve in JavaScript
• How to get the days between 2 dates in JavaScript
• How to upload a file using Fetch
• How to format a date in JavaScript
• How to iterate over object properties in JavaScript
• How to calculate the number of days between 2 dates in JavaScript
• How to use top-level await in ES Modules
• JavaScript Dynamic Imports
• JavaScript Optional Chaining
• How to replace white space inside a string in JavaScript
• JavaScript Nullish Coalescing
• How to flatten an array in JavaScript
• This decade in JavaScript
• How to send the authorization header using Axios
• List of keywords and reserved words in JavaScript
• How to convert an Array to a String in JavaScript
• How to remove all the node_modules folders content
• How to remove duplicates from a JavaScript array
• Let vs Const in JavaScript
• The same POST API call in various JavaScript libraries
• How to get the first n items in an array in JS
• How to divide an array in multiple equal parts in JS
• How to slow down a loop in JavaScript
• How to load an image in an HTML canvas
• How to cut a string into words in JavaScript
• How to divide an array in half in JavaScript
• How to write text into to an HTML canvas
• How to remove the last character of a string in JavaScript
• How to remove the first character of a string in JavaScript
• How to fix the TypeError: Cannot assign to read only property 'exports' of object '#<Object>' error
• How to create an exit intent popup
• How to check if an element is a descendant of another
• How to force credentials to every Axios request
• How to solve the "is not a function" error in JavaScript
• Gatsby, how to change the favicon
• Loading an external JS file using Gatsby
• How to detect dark mode using JavaScript
• Parcel, how to fix the `regeneratorRuntime is not defined` error
• How to detect if an Adblocker is being used with JavaScript
• Object destructuring with types in TypeScript
• The Deno Handbook: a concise introduction to Deno 🦕
• How to get the last segment of a path or URL using JavaScript
• How to shuffle elements in a JavaScript array
• How to check if a key exists in a JavaScript object
• Event bubbling and event capturing
• event.stopPropagation vs event.preventDefault() vs. return false in DOM events
• Primitive types vs objects in JavaScript
• How can you tell what type a value is, in JavaScript?
• How to return multiple values from a function in JavaScript
• Arrow functions vs regular functions in JavaScript
• In which ways can we access the value of a property of an object?
• What is the difference between null and undefined in JavaScript?
• What's the difference between a method and a function?
• What are the ways we can break out of a loop in JavaScript?
• The JavaScript for..of loop
• What is object destructuring in JavaScript?
• What is hoisting in JavaScript?
• How to change commas into dots with JavaScript
• The importance of timing when working with the DOM
• How to reverse a JavaScript array
• How to check if a value is a number in JavaScript
• How to accept unlimited parameters in a JavaScript function
• JavaScript Proxy Objects
• Event delegation in the browser using vanilla JavaScript
• The JavaScript super keyword
• Introduction to XState
• Are values passed by reference or by value in JavaScript?
• Custom events in JavaScript
• Custom errors in JavaScript
• Namespaces in JavaScript
• A curious usage of commas in JavaScript
• Chaining method calls in JavaScript
• How to handle promise rejections
• How to swap two array elements in JavaScript
• How I fixed a "cb.apply is not a function" error while using Gitbook
• How to add an item at the beginning of an array in JavaScript
• Gatsby, fix the "cannot find module gatsby-cli/lib/reporter" error
• How to get the index of an item in a JavaScript array
• How to test for an empty object in JavaScript
• How to destructure an object to existing variables in JavaScript
• The Array JavaScript Data Structure
• The Stack JavaScript Data Structure
• JavaScript Data Structures: Queue
• JavaScript Data Structures: Set
• JavaScript Data Structures: Dictionaries
• JavaScript Data Structures: Linked lists
• JavaScript, how to export a function
• JavaScript, how to export multiple functions
• JavaScript, how to exit a function
• JavaScript, how to find a character in a string
• JavaScript, how to filter an array
• JavaScript, how to extend a class
• JavaScript, how to find duplicates in an array
• JavaScript, how to replace an item of an array
• JavaScript Algorithms: Linear Search
• JavaScript Algorithms: Binary Search
• JavaScript Algorithms: Selection Sort
• JavaScript Algorithms: Quicksort
• JavaScript Algorithms: Merge Sort
• JavaScript Algorithms: Bubble Sort