JavaScript Cheat Sheet
JavaScript programming reference guide
JavaScript Cheat Sheet
Quick reference guide for JavaScript programming. Click the copy button to copy any command.
117
Total Commands
117
Filtered Results
Variables
| Command | Copy | Description |
|---|---|---|
let x = 5 | Declare variable (block scope) | |
const x = 5 | Declare constant | |
var x = 5 | Declare variable (function scope) |
Data Types
| Command | Copy | Description |
|---|---|---|
typeof x | Get type of variable | |
Number(x) | Convert to number | |
String(x) | Convert to string | |
Boolean(x) | Convert to boolean |
Strings
| Command | Copy | Description |
|---|---|---|
s.length | String length | |
s.toUpperCase() | Convert to uppercase | |
s.toLowerCase() | Convert to lowercase | |
s.trim() | Remove whitespace | |
s.split(",") | Split into array | |
s.replace("old", "new") | Replace substring | |
s.includes("text") | Check if contains text | |
s.startsWith("pre") | Check start | |
s.endsWith("suf") | Check end | |
s.slice(0, 5) | Extract substring | |
`Hello ${name}` | Template literal |
Arrays
| Command | Copy | Description |
|---|---|---|
arr.length | Array length | |
arr.push(item) | Add to end | |
arr.pop() | Remove from end | |
arr.shift() | Remove from start | |
arr.unshift(item) | Add to start | |
arr.splice(index, count) | Remove/replace items | |
arr.slice(start, end) | Extract portion | |
arr.concat(arr2) | Combine arrays | |
arr.join(",") | Join to string | |
arr.reverse() | Reverse array | |
arr.sort() | Sort array | |
arr.indexOf(item) | Find index | |
arr.includes(item) | Check if includes | |
arr.find(fn) | Find first matching | |
arr.filter(fn) | Filter array | |
arr.map(fn) | Transform array | |
arr.reduce(fn, initial) | Reduce to single value | |
arr.forEach(fn) | Iterate over array | |
[...arr] | Spread operator |
Objects
| Command | Copy | Description |
|---|---|---|
obj.key | Access property | |
obj["key"] | Access with bracket notation | |
obj.key = value | Set property | |
delete obj.key | Delete property | |
Object.keys(obj) | Get all keys | |
Object.values(obj) | Get all values | |
Object.entries(obj) | Get key-value pairs | |
{...obj} | Spread object | |
Object.assign({}, obj) | Copy object |
Functions
| Command | Copy | Description |
|---|---|---|
function name() {} | Function declaration | |
const name = function() {} | Function expression | |
const name = () => {} | Arrow function | |
function name(a = 1) {} | Default parameter | |
function name(...args) {} | Rest parameters | |
return value | Return value |
Conditionals
| Command | Copy | Description |
|---|---|---|
if (condition) {} | If statement | |
else if (condition) {} | Else if statement | |
else {} | Else statement | |
condition ? true : false | Ternary operator | |
switch (x) { case 1: break; } | Switch statement |
Loops
| Command | Copy | Description |
|---|---|---|
for (let i = 0; i < 10; i++) {} | For loop | |
for (let item of array) {} | For...of loop | |
for (let key in object) {} | For...in loop | |
while (condition) {} | While loop | |
do {} while (condition) | Do...while loop | |
break | Exit loop | |
continue | Skip iteration |
DOM Manipulation
| Command | Copy | Description |
|---|---|---|
document.getElementById("id") | Get element by ID | |
document.querySelector("selector") | Query selector | |
document.querySelectorAll("selector") | Query all | |
element.textContent | Get/set text content | |
element.innerHTML | Get/set HTML content | |
element.classList.add("class") | Add CSS class | |
element.classList.remove("class") | Remove CSS class | |
element.classList.toggle("class") | Toggle CSS class | |
element.style.property = value | Set inline style | |
element.setAttribute("attr", "value") | Set attribute | |
element.getAttribute("attr") | Get attribute | |
document.createElement("div") | Create element | |
parent.appendChild(child) | Append child | |
parent.removeChild(child) | Remove child |
Events
| Command | Copy | Description |
|---|---|---|
element.addEventListener("click", fn) | Add event listener | |
element.removeEventListener("click", fn) | Remove event listener | |
event.preventDefault() | Prevent default action | |
event.stopPropagation() | Stop event bubbling |
Promises
| Command | Copy | Description |
|---|---|---|
new Promise((resolve, reject) => {}) | Create promise | |
promise.then(fn) | Handle success | |
promise.catch(fn) | Handle error | |
promise.finally(fn) | Always execute | |
Promise.all([p1, p2]) | Wait for all | |
Promise.race([p1, p2]) | Wait for first |
Async/Await
| Command | Copy | Description |
|---|---|---|
async function name() {} | Async function | |
await promise | Wait for promise | |
try {} catch(e) {} | Try-catch block |
Fetch API
| Command | Copy | Description |
|---|---|---|
fetch(url) | Make HTTP request | |
fetch(url, {method: "POST"}) | POST request | |
response.json() | Parse JSON response | |
response.text() | Get text response |
JSON
| Command | Copy | Description |
|---|---|---|
JSON.stringify(obj) | Convert to JSON string | |
JSON.parse(str) | Parse JSON string |
Math
| Command | Copy | Description |
|---|---|---|
Math.random() | Random number 0-1 | |
Math.floor(x) | Round down | |
Math.ceil(x) | Round up | |
Math.round(x) | Round to nearest | |
Math.max(a, b) | Maximum value | |
Math.min(a, b) | Minimum value |
Date
| Command | Copy | Description |
|---|---|---|
new Date() | Create date object | |
date.getFullYear() | Get year | |
date.getMonth() | Get month (0-11) | |
date.getDate() | Get day of month | |
date.getTime() | Get timestamp | |
Date.now() | Current timestamp |
Console
| Command | Copy | Description |
|---|---|---|
console.log(x) | Log to console | |
console.error(x) | Log error | |
console.warn(x) | Log warning | |
console.table(arr) | Display as table |
Timing
| Command | Copy | Description |
|---|---|---|
setTimeout(fn, ms) | Execute after delay | |
setInterval(fn, ms) | Execute repeatedly | |
clearTimeout(id) | Cancel timeout | |
clearInterval(id) | Cancel interval |
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