JavaScript Functions

JavaScript Functions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],You.learn() Jupiter IT

Why? ,[object Object],[object Object],[object Object],Jupiter IT

The Basics var square = function ( x ){ return x * x ; } square(5) Function reference Function keyword Arguments Code body Return value Jupiter IT

3 Ways to Declare a Function var f = function (){ alert ( 'hi' )} function f (){ alert ( 'hi' )} window . f = function (){ alert ( 'hi' )} Jupiter IT

Everything is an Object I ask "girl can I have closures, canvas, advanced features for my project?" You say "sure, but keep it simple, everything is an object" I say "JavaScript you've come a long way from copy-paste hacks" You blush "I know, but please, call me AJAX" -- Digital Crush Jupiter IT var f = function ( a , b ){ return a - b }; var g = “hi”; var h = 1;

Functions are First Class ,[object Object],[object Object],[object Object],var f = function ( a , b ){ return a - b }; [1,2,3,4].sort ( f ); var g = function (){ return true ;} function bark (){ return function (){ alert ( 'bark' ); } } Jupiter IT

Functions are First Class ,[object Object],[object Object],var obj = { func : function (){ alert ( 'i am a function' ); } } obj.func(); var a = []; a [ 0 ] = function (){ return true ;} a[0](); Jupiter IT

Passing Arguments ,[object Object],[object Object],function change ( obj ){ obj . a = obj . val + 1 ; } var obj = { a : 1 }; change ( obj ); alert ( obj . a ); function change ( x ){ x = x + 1 ; } var a = 1 ; change ( a ); alert ( a ); Jupiter IT // alerts 1 // alerts 2

Context ,[object Object],function f (){ this . barkCount ++; } f(); var dog = { barkCount : 0 , bark : function (){ this . barkCount ++; } } dog . bark (); Jupiter IT

Context ,[object Object],[object Object],[object Object],doYourBusiness . call ( dog , 1 , 2 ); doYourBusiness . apply ( dog , [ 1 , 2 ]); dog . doYourBusiness ( 1 , 2 ); Jupiter IT

Arguments ,[object Object],function sum (){ var s = 0 ; for ( var i = 0 ; i < arguments . length ; i ++){ s += arguments [ i ]; } return s ; } alert ( sum ( 1 , 2 , 3 )); Jupiter IT // alerts 6

Arguments ,[object Object],function f ( a , b ){ if ( arguments . length != f . length ) alert ( 'wrong nbr of args' ); else alert(‘right nbr of args’); } f ( 1 ); f ( 1,2 ); Jupiter IT // alerts “wrong nbr of args” // alerts “right nbr of args”

Closures ,[object Object],var a = 1 ; function f ( arg ){ alert ( a ); var b = 1 ; function g (){ alert ( a + b ); } g(); } Jupiter IT

Closures ,[object Object],var Dog = function (){ var breed ; this . getBreed = function (){ return breed ; } this . setBreed = function ( newBreed ){ breed = newBreed ; } } var dog = new Dog (); dog . setBreed ( 'doberman' ); alert ( dog . getBreed ()); dog.breed Jupiter IT

Closures ,[object Object],Todo = { markAsCompleted : function ( task_name ){ MVC . Ajax ( '/complete/' + task_name , { onSuccess : function ( transport ){ alert ( task_name ); } }) } } Jupiter IT

Closures ,[object Object],[object Object],( function (){ var count = 0 ; $ ( 'some_div' )[ 0 ]. click ( function (){ count = count + 1 ; alert ( count ); }) })(); Jupiter IT

Closures ,[object Object],[object Object],var a = {}; for ( var i = 0 ; i < 3 ; i ++){ a [ i ] = function (){ alert ( i )}; } a [ 0 ](); a [ 1 ](); a [ 2 ](); Jupiter IT // alerts 2 // alerts 2 // alerts 2

Closures ,[object Object],[object Object],var a = {}; for ( var i = 0 ; i < 3 ; i ++){ ( function ( j ){ a [ j ] = function (){ alert ( j )}; })( i ) } a [ 0 ](); a [ 1 ](); a [ 2 ](); Jupiter IT // alerts 0 // alerts 1 // alerts 2

Two Things to Remember ,[object Object],[object Object],Jupiter IT Poppin' bottles with Document Object Models, So many lonely nights with Prototype. Opera, IE, Firefox, or Chrome, I write cross browser code and give you a home. -- Digital Crush

JavaScript Functions

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