functions intro

Functionsexecutes code chunks when called

http://www.w3schools.com/js/js_functions.asp

Thursday, October 1, 2009



surprise!you already have been using them since your first line of codedocument.write, alert, prompt, confirm, parseInt, etc.


defining a function

function foo() { // some code}


defining a function


function keyword


defining a function


function keyword function name


defining a function


function keyword function name parenthesis


defining a function



start of function


defining a function



start of functionend of function


braces always mean start and stop

(if, else if, else, for, for...in, while, functions, objects


calling a function// define function foo // for later usefunction foo() { // some code}

// call the function and // run the code inside itfoo();


functions are called using parenthesis and the function name

( )


calling a function// define function foo // for later usefunction foo() { // some code}

// does not execute functionfoo;

// executes functionfoo();


var number_1 = 5;var number_2 = 10;var sum = number_1 + number_2;

function foo() { alert('This will never alert.');}

alert(sum);

// only sum will be alerted// the string inside foo function does // not because foo was never called

the code inside functions only executes when the function is called


functions can return values

// define the functionfunction name() { return 'John Nunemaker';}

// call the functionvar name = name();// name variable is now 'John Nunemaker'


the instant a return statement is found, the function returns and stops execution


function demoReturn() { return; // this will never be called alert('hi');}

// will not alert ‘hi’demoReturn();

return doesn’t have to return a value


functions can havea parameter

// define the functionfunction name(name) { return 'The name was: ' + name;}

// call the functionvar message = name('Ron Burgandy');// message variable is now 'The name was: Ron Burgandy'

// call the function again with different namemessage = name('Veronica Corningstone');// message variable is now 'The name was: Veronica Corningstone'






name is a parameter






name is a parameter

‘Ron Burgandy’ is an argument

‘Veronica Corningstone’ is an argument


functions can have multiple parameters

// define the functionfunction fullName(first_name, last_name) { return first_name + ' ' + last_name;}

var wes = fullName('Wes', 'Mantooth');// wes variable is now 'Wes Mantooth'

var brian = fullName('Brian', 'Fantana');// brian variable is now 'Brian Fantana'


philosophical tidbitparameter - name of value to be used in function

argument - value passed in when function called


camelCaseFunctionNames


naming conventions

// variables use underscoresvar full_name = 'John Nunemaker';

// functions use camel case with lower firstfunction fullName() { return 'John Nunemaker';}


function can be made up of any code

function demoWithLoop(loops) { for (var i=0; i < loops; i++) { alert("Why'd you have to wait..."); }}

// two alertsdemoWithLoop(2);


functions, ifs, loopsfunction demoWithLoop(loops) { if (loops > 10) { alert('DO NOT WANT!'); } else { for (var i=0; i < loops; i++) { alert("Why'd you have to wait..."); } }}

// alert DO NOT WANT!demoWithLoop(11);

// 4 alerts of Why'd you have to wait...demoWithLoop(4);


functions, ifs, loops, returnfunction demoWithLoop(loops) { if (loops > 10) { alert('DO NOT WANT!'); return; } for (var i=0; i < loops; i++) { alert("Why'd you have to wait..."); }}

// alert DO NOT WANT!demoWithLoop(11);

// 4 alerts of Why'd you have to wait...demoWithLoop(4);


assignment06http://teaching.johnnunemaker.com/capp-30550/sessions/functions/


http://teaching.johnnunemaker.com/capp-30550/sessions/functions/

http://teaching.johnnunemaker.com/capp-30550/sessions/functions/

functions intro

Technology