A JavaScript Cheat Sheet: A Reference Guide of Functions

A

alert	Shows a modal window that has a specific message and an OK button.
array.length	Returns the length of an array
array.map	Invokes a function for every element of an array (in order)
array.push	Adds elements to an array and declares a new length
array.sort	Sorts array elements in either alphabetic or ascending, and descending or ascending order

B

boolean	Returns either true or false based on the specified statement or condition
break and continue	Break stops a loop from running. Continue skips an iteration of a loop

C

className	Sets or returns the name of a class of an HTML element
confirm	Displays a specified message in a dialog box, containing OK and CANCEL buttons

D

decodeURIComponent

Decodes URI components

I

if	Runs code when a condition is met
indexOf	Searches the array for a specified item, then returns its position
innerHTML	Sets or returns the HTML content inside an element

M

Math	Performs mathematical calculations
Math.random	Generates a random number from 0 (inclusive) up to but not including 1 (exclusive)

N

Number	Converts object arguments into numbers
number.toString	Converts a number to a string

O

onclick	An event that occurs when the user clicks on an element
onload	Transpires when an object is loaded

R

replace

Searches a string for a regular expression or a specified value and returns a string with replaced specified values

S

setAttribute	Adds a specified attribute to an element, giving the attribute a certain value
setInterval	Executes a specified function multiple times at set time intervals specified in milliseconds (1000ms = 1second)
setTimeout	Calls a function after the time specified in milliseconds (1000 ms = 1 second) has passed
slice	Returns selected elements of an array into a new array object
splice	Adds or removes items from an array
string.includes	Determines whether a string contains characters of a specified string or not
string.indexOf	Returns the position of the first occurrence of a specified value inside a string variable
string.split	Splits a data string into a substrings array and returns the new array
style.display	Sets or returns the display type of a specified element
submit	Submits an HTML form
substr	Extracts parts of a string
substring	Extracts the symbols between two indexes and returns a data string
switch	Executes actions for various conditions

F

for	Runs a piece of code a set number of times
forEach	Applies a specified function for every item in a particular array individually

L

location.reload

Reloads the current web page

P

parseInt	Converts a string to an integer
prompt	Displays a dialog box, which would require a person to type in input

T

test	Looks for a match inside a string variable
throw, try and catch	The try and catch block lets you set an error handling code: try defines a code of block that will be tested for errors, and catch defines a code of block that handles the error
toLowerCase	Converts all letters in a specified string lowercase
toUpperCase	Converts all letters in a specified string to uppercase

U

use strict

Sets JavaScript code to be executed in strict mode

W

while	Executes a block of code as long as the defined condition is true
window.history	Holds information about internet browsers history
window.location	Gets information about the current address (URL)
window.navigator	Contains the information about the user's browser
window.screen	Holds the information about the screen of the browser (for instance, the screen width and height)