looping

loopsexecuting code over and over again

Thursday, September 24, 2009

for looploop a specified number of times;the only loop you need to know

http://www.w3schools.com/jS/js_loop_for.asp




for (var i=0; i < 5; i++) { // some code to run}



before any loops



before each loop



after each loop


for (var i=0; 0 < 5; i++) { // i would be 0}


for (var i=0; 5 < 5; i++) { // condition false so this // would never happen}


var colors = ['red', 'green', 'blue'];

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


var colors = ['red', 'green', 'blue'];

for(var i=0, length=colors.length; i < length; i++) { colors[i];}


var colors = ['red', 'green', 'blue'];var length = colors.length;

for(var i=0; i < length; i++) { colors[i];}


while looploop while a condition is true

http://www.w3schools.com/JS/js_loop_while.asp




var i = 0;

while (i < 5) { // some code to run i++;}


var i = 0;

while (i < 5) { // some code to run i++;}

before each loop


var i = 0;

while (0 < 5) { // i would be 0 i++; // i would be 1}


var i = 0;



var i = 0;

while (5 < 5) { // condition is false so // this would never happen i++;}


for..in looploop through the properties of an object

http://www.w3schools.com/jS/js_loop_for_in.asp




for (property in object) { // some code here}


var person = { name: 'John Nunemaker', age: 27, married: true, cat_owner: 'unfortunately'};

for (property in person) { property; person[property];}



for (property in person) { property; // ‘name’ person[property]; // ‘John Nunemaker’}



for (property in person) { property; // ‘age’ person[property]; // 27}



for (property in person) { property; // ‘married’ person[property]; // true}



for (property in person) { property; // ‘cat_owner’ person[property]; // ‘unfortunately’}


breakbreak the current loop

and continue with code after loop if any

http://www.w3schools.com/jS/js_break.asp




think “stop looping right now”


for (var i=0; i < 5; i++) { if (i === 2) { break; } i;}


for (var i=0; 0 < 5; i++) { if (0 === 2) { // false break; } i; // 0}


for (var i=0; 1 < 5; i++) { if (1 === 2) { // false break; } i; // 1}


for (var i=0; 2 < 5; i++) { if (2 === 2) { // true break; // breaks out of loop } i; // never gets here}


most common use is switch statement, but good to know it works elsewhere


continuebreak the current loop

and continue with the next value





think “skip current loop”


for (var i=0; i < 3; i++) { if (i === 1) { continue; } i; // comment}


for (var i=0; 0 < 3; i++) { if (0 === 1) { // false continue; } i; // 0}


for (var i=0; 1 < 3; i++) { if (1 === 1) { // true continue; } i; // never gets here}


for (var i=0; 2 < 3; i++) { if (2 === 1) { // false continue; } i; // 2}


for (var i=0; 3 < 3; i++) { // never gets here if (i === 1) { continue; } i;}


assignment04http://teaching.johnnunemaker.com/capp-30550/sessions/looping/


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

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

looping

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