Javascript Regular Expression Cheat Sheet

Posted : admin On 1/29/2022

For more information, see “JavaScript for impatient programmers”: lookahead assertions, lookbehind assertions. A word of caution about regular expressions # Regular expressions are a double-edged sword: powerful and short, but also sloppy and cryptic. Regular Expressions Cheat Sheet by DaveChild - Created Date: 4237Z.

  1. Javascript Regular Expression Cheat Sheet
  2. Javascript Regular Expression Cheat Sheet Answer

Types of variables

var i = 123; integer
var f=0.2 real number
var t='texte' string
var a=[1, 'deux', 'trois']array
var m={1:'un', 'deux':2}map, associative array
function x() {}object

Event handlers


onAbort loading stopped
onBlurfocus lost
onChange content modified
onClick clicked
onDblClick clicked twice
onDragDrop moved
onErrornot loaded
onFocus focus entered
onKeyDownkey depressed
onKeyPress key pressed
onKeyUp key released
onLoad just after loading
onMouseDown mouse button depressed
onMouseMovemouse moved
onMouseOut mouse exited
onMouseOvermouse on the element
onMouseUpmouse button released
onReset reset form button clicked
onResize size of page changed
onSelect element selected
onSubmit submit form button clicked
onUnloadpage exited

Methodes of object (inherited by all objects)


toString()convert to a string
toLocaleString()convert to a localized string
valueOf() get the value

Date methods

new Date()constructor, arguments: milliseconds, string, list
getDate()day of the month
getDay() day of the week
getTime() number of milliseconds since 1/1/1970
getYear() and getMonth/Hour/Minutes/Seconds

String methods

charAt() character at the given position
charCodeAt()code of a character
concat() concatenate with the argument
indexOf() position of a character
lastIndexOf() position from the end
localeCompare() localized comparison
matchapply a regular expression()
replace() replace a substring
search()search a substring
slice() extract a part
split() cut to build an array with parts
substring() extract a part
toLowerCase() convert to lowercase
toUpperCase() convert to uppercase
toLocaleLowerCase()localized lowercase
toLocaleUpperCaselocalized uppercase ()

Array, index and methods

a['one']=1 assignment by indice assignment by attribute
delete a['one'] deletion by indice
delete deletion by attribute
for(var k in a) {} iteration on the content
concat() add a second array
join() concatenate the elements into a string
push() add an element
pop()get and remove the last element
reverse() invert the order of elements
shift() insert an element at start
slice() extract a sub-array
spliceinsert an array ()
sort() sort the elements
toString() return the array as a string
unshift()get and remove the first element

Number methods

new Number()constructor with a decimal/hexa/string argument
toString() convert to a string
toExponential() exponential form
toPrecision() convert to a given number of decimals

Function (is also an object)

function x(a, b) { return y; } declaration
y = x(1, 'two') call
var y = new x(1, 'two') declaring a instance
x.prototype.methodx =
function() { }
adding a method

Built-in functions

eval() evaluate an expression
parseInt()convert a string to an integer
parseFloat() convert a string to a floating number
isNaN() check if the content of a variable is valid
ifFinite() check for overflow
decodeURI() convert to a string
decodeURIComponent()decode a component of the URL
encodeURI() convert to file name
encodeURIComponent()encode a component to URL
escape() convert to URL parameters
unescape() convert parameters to normal string

Regular expressions, suffixes

Javascript Regular Expression Cheat Sheet

Javascript Regular Expression Cheat Sheet

g global
i case-insensitive
s single line
m multi-lines

Regular expressions, masks

Javascript Regular Expression Cheat Sheet Answer

^ start of string
$end of string
!() but this group
. any character
(x y)either x or y
[xyz] among x y or z
[^xyz] any but x y or z
a? may holds a once
a+ at least a once
a* zero or several times a
a{5} five times a
a{5,} at least five times a
a{1, 4}a between 1 and 4 times