Intro to Loops Continued

Diving Deeper into JavaScript Control Statements (Loops)

- Professor Flo Davis… Mwahaha

Increment/Decrement Operators

i++ is the same as i = i + 1;

i- - is the same as i = i -1;

Increment Operator Syntax x++ or ++x

//PostFix

var x = 3;

y = x++ // y =3, x=4

//PreFix

var a = 2;

b = ++a; // a = 3, b =3

Working Example https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators

Increment Operator Example

var x = 5;

x++;

var z = x;

console.log(z) // z = 6;

Working Example http://www.w3schools.com/js/tryit.asp?filename=tryjs_oper_increment

Decrement OperatorThe decrement operator subtracts

Syntax x - - or - - x

// Postfix

var x = 3;

y = x - - ; y = 3, x = 2

// Prefix

var a = 2;

b = - - a; // a = 1, b = 1

Working Example https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators

Decrement Operator Example

var x = 5;

x- - ;

var z = x; // z = 4

Working Example http://www.w3schools.com/js/tryit.asp?filename=tryjs_oper_decrement

The For Loopfor(initialize; test; increment/decrement) { // Code Block//}

Example Standard For Loop

for(var i = 0; i<10; i++){console.log(i);} // This will print the numbers from 1 through 10.

We use i, because that is short for index

For Loop Example (Decrement)

for(var i=10; i>5; i- - ){ console.log(i);}

REMEMBER: i++ or i - - is the same as i+=1, or i -=1, code what ever works for you best.

Looping Through An Array with For Loop

var Professor = [‘Florence’, ‘Davis’];

for(var i =0; i<Professor.length;i++){console.log(Professor[i]);}

// Let’s refactor code and make it cleaner

var Professor = [‘Florence’, ‘Davis’];

var length = Professor.length;

for(var i = 0; i<length;i++){console.log(Professor[i]);}

Oh…It’s Been AwhileWhile Loops

While Loopswhile(condition) {// statement}

Example var i = 0;

while(i<10){ console.log(i + ‘….. this will go on until we hit 10’);

i += 1; // same as i++ throwing you for a loop making sure your paying attention haha :) , remember they can be used interchangeably whatever you prefer.

If you need further explanations don’t forget our good friends at Mozilla: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/while

While Loops IIvar n = 0;

while(n < 3) { console.log(“Looping,”);

n++;}

// Will print looping 3 times

Looping…

looping…

Looping…

–Johnny Appleseed

“Happy Coding.”