javascript Cheat Sheet

Value Types

Number
Any numeric value
String
Characters inside quote marks
Boolean
True or False
Null
Empty and meanin­gless
Object
Any value associated with the object
Function
Value returned by a function

Operators

x + y (numeric)
Adds x and y together
x + y (string)
Concat­inates x and y together
x – y
Subtracts y from x
x * y
Multiplies x and y together
x / y
Divides x by y
x % y
Modulus: The remainder when x is divided by y
x++, ++x
Adds one to x
x–, –x
Subtracts one from x
-x
Reverses the sign on x

Assign­ments

x = y
Sets x to the value of y
x += y
Same as x = x + y
x -= y
Same as x = x – y
x *= y
Same as x = x * y
x /= y
Same as x = x / y
x %= y
Same as x = x % y

Adding to an array

.length property
Adds one value to the end of an array
push()
Adds one or more items to the end of an array
unshift()
Adds one or more items to the beginning of an array.

Misc

parseInt()
Takes a value and tries to convert it to an integer
isNaN()
Returns true if something is not a number.
setTim­eout()
Specify that am action should occur on a particular schedule
Math.floor
Rounds a number down
Math.r­andom
Generaters a random number between 0 and 1
getEle­men­tsB­yTa­gName()
getEle­men­tById()
getEle­men­tsB­yCl­ass­Name()
elemen­t.i­nne­rHTML
returns all the HTML between the opening and closing tags
elemen­t.n­odeType
property, returns the number of the node type
elemen­t.c­hil­dNodes
A node list of child nodes that are indexed numeri­cally, and appear in source order.
elemen­t.c­hil­dNo­des.length
Returns the number of child nodes of the element

Event Handlers

onabort
The user aborted loading the page
onblur
The user left the object
onchange
The user changed the object
onclick
The user clicked an object
onerror
The script encoun­tered an error
onfocus
The user made an object active
onload
The object finished loading
onmous­eover
The cursor moved over an object
onmouseout
The cursor moved off an object
onselect
The user selected the contents of an object
onsubmit
The user submitted a form
onunload
The user left the page
onmove
The window is moved
onmous­edown
A mouse button is pressed down
onmouseup
A mouse button is released
onmous­emove
The mouse moves
ondblclick
A double click of a mouse button
onclick
A single click (down and then up) of a mouse button
onreset
A reset button is clicked on a form
onkeydown
Triggered when a key is pressed down
onkeyup
Triggered when a key is released
onkeypress
Triggered when a key is pressed and then released

Compar­isons

x == y
Returns true if x and y are equal
x === y
Returns true if x and y are identical
x != y
Returns true if x and y are not equal
x !== y
Returns true if x and y are not identical
x > y
Returns true if x is greater than y
x >= y
Returns true if x is greater than or equal to y
x < y
Returns true if x is less than y
x <= y
Returns true if x is less than or equal to y
x && y
Returns true if both x and y are true
x || y
Returns true if either x or y are true
!x
Returns true if x is false

Remove item from an array

pop()
Removes the last item from the array
shift()
Removes the first item from the array
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