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Javascript

Script Tags

The second and fourth lines of HTML comments are from the days of dealing with old browsers that ignore the <script>-tag, and would otherwise try to print out what's within those tags. <script type="text/javascript"> <!-- alert("script goes here"); // --> </script> <script type="text/javascript" defer>

Functions

With Arguments

function addMeUp(ouncesOfWater,glassCapacity,unit) { howFull = ouncesOfWater/glassCapacity; alert('The glass is ' + howFull + ' ' + unit + ' full.'); } addMeUp(5,10,'ounces');

With No Arguments

function pringles() { alert('Pop.'); }

With Returned Values

function calculate(cats,dogs) { pets = cats+dogs; return pets; } var numberOfPets = calculate(cats,dogs);

Anonymous Functions

function() { alert("I have no name."); }

Strings

var noimnot = 'I\'m currently "studying".'

Statements: Conditions

If-Else

if (a > 8) { //somecodehere } else if (a < 3) { //somecodehere } else { //somecodehere } if (b == 'blue') { //somecodehere } else if (b != 'purple') { //somecodehere } else { //somecodehere } if (a <= 5) { //somecodehere } else if (a >= 6) { //somecodehere } else { //somecodehere }

For

for (var i=1; i<=5; i++) { nfactorial = nfactorial * i; }

For Through Properties of an Object

for (var i in object) { //somecodehere }

Forms

Running a function before submitting

<form action="dothis.pl" onsubmit="return validatescript()"> function validatescript() { if (fieldmonthvalue > 12 | field1value < 1) { alert("Please put a valid month value."); return false; } else if (fieldyearvalue > 3000) { alert("We do not support this service beyond this millenium."); return false; } // No errors in this form, so submit. return true; }

Accessing form elements directly

<form name="profile" action="dothis.pl" onsubmit="return somevalidationscript()"> <input type="text" name="name" /> <input type="text" name="gender" /> <input type="text" name="height" /> <input type="text" name="weight" /> </form> <script type="text/javascript"> document.profile.name document.profile.gender document.profile.height document.profile.weight </script>

Accessing form methods

<form name="profile" action="dothis.pl"> <input type="text" name="name" /> </form> <script type="text/javascript"> document.forms[0].submit() document.forms[0].reset() document.forms[0].action = 'dothis.pl'; </script>

Pre-written Functions

.length - Length of String or Number

var thisLength = 'I am a long and windy road'.length; var thatLength = somevariable.length;

.toString() - Convert number to string

var somenumber = 300; var numberAsString = somenumber.toString(); // numberAsString = 300 the string, not 300 the number

Convert string to number

var numberAsString = '42'; var actualNumber = numberAsString * 1; // actualNumber = 42 the number, not 42 the string // because it converts the string to a number (or NaN if it's text) when multiplying

Concatenating a number to a string

var numberAsString = '123'; var sum = numberAsString + 4; // sum = 1234 because the + tries to concatenate string instead of adding the math var total = 'abc123' + 4 // total = abc1234

Objects

Method vs. Property

object.method()

someObject.methodDoesThings() - Something happens when it's called (the method does something).

object.property

someObject.propertyIsValue - You get (or set) this value when it's called (the property is something - a number, string, boolean, etc.)

Initializing an Object

var person = new Object;

Adding and Defining Properties of an Object

person.mood = "thrilled";

Calling Methods of an Object

document.write('I like my soups.');

Object Check

It is a good idea to check whether the object exists in a given browser. if (window.focus) { window.focus(); }

Object Check to Exit a Function

function someFunction() { var isItSupported = document.createElement && document.getElementsByTagName; if (!isItSupported) { return; } else { var someTagArray = document.getElementsByTagName("p"); } }

This

function someFunction() { this.style.color = "#ccc"; //The "this" refers to the "window" (global) object } a.onclick = someFunction; // onclick property becomes method // The "this" refers to the "a" element. <a onclick="this.style.color = '#ccc';">The "this" refers to the "a" element.</a> <a onclick="someFunction()">The onclick contains the function call and executes it, and "this" refers to the "window"" object.</a>

Associative Arrays (a.k.a. Hashes)

The array associates each key with a value. person["mood"] // is like saying, person.mood, in person.mood = "thrilled"; // "mood" is the key, which has a value "thrilled"

For/in Statement

Go through all properties of the "person" object (i.e. go through all keys in the associative array "person") for (var i in person) { if (person[i] == 'mouseover') { someFunction(i); } } // above is the equivalent of saying: if (person.mood == 'mouseover') { someFunction('mood'); } if (person.energy == 'mouseover') { someFunction('energy'); }

Popups

<script type="text/javascript"> function poppy(url) { popwindow = window.open(url,"somename","height=200,width=150"); if (window.focus) { popwindow.focus(); } return false; } </script> <a href="terms.html" onclick="return poppy('terms.html')">Launch popup window.</a>

Events

Inline Event Registration

<a href="gogogo.html" onclick="someFunction()">Inline event registration</a>

Traditional Event Registration

someelement.onclick = functionOne; someelement.onclick = functionToo; // second one overrides the first // thus functionToo() executes when the user clicks on the element

Traditional Event Registration - Multiple

someelement.onclick = function () {functionOne(); functionToo()} // registers a function that executes both other functions

Advanced Event Registration

someelement.addEventListener("click", someFunction, false); // "click" is the event type

Mouse Events

Onmouseover - hovering over element

<a href="javascript:void(null)" onmouseover="alert('mouseover')">Linkie</a>

Onmouseout - hovering off of element

<a href="javascript:void(null)" onmouseout="alert('mouseout')">Linkie</a>

Onmousedown - holding click down

<a href="javascript:void(null)" onmousedown="alert('mousedown')">Linkie</a>

Onmouseup - releasing click button

<a href="javascript:void(null)" onmouseup="alert('mouseup')">Linkie</a>

Onclick = onmousedown + onmouseup

<a href="javascript:void(null)" onclick="alert('click')">Linkie</a>

Onmousemove

<a href="javascript:void(null)" onmousemove="alert('mousemove')">Linkie</a>

window.status

In browsers like Firefox, this is disabled by default. <a href="paged.html" onmouseover="window.status = 'Text in a status bar'; return true" onmouseout="window.status = 'Back to normal'; return true">Linkie</a>

Offsets/Position

//pixels from the left someobj.offsetLeft //pixels from the top someobj.offsetTop //how many pixels its height is at the moment someobj.offsetWidth //how many pixels its width is at the moment someobj.offsetWidth someobj.offsetParent function getOff() { someobj = document.getElementById("testing"); return someobj.offsetWidth; }

Getting and Setting Styles

someObject.currentStyle someObject.getComputedStyle document.styleSheet // an array of all linked and embedded stylesheets document.styleSheets[0].cssRules['PRE.test'] // Gecko/Webkit browsers document.styleSheets[0].rules['PRE.test'] // IE someelement.style.color = "#ccc"; someelement.style.backgroundColor = "#ccc"; someelement.style.setProperty("color","#ccc",null);

Opacity

someObject.style.opacity = 1; someObject.style.filter = "alpha(opacity='1')";

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