Looping - Speaker Deck

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loops executing code over and over again Thursday, September 24, 2009

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Thursday, September 24, 2009

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for loop loop a speciﬁed number of times; the only loop you need to know http://www.w3schools.com/jS/js_loop_for.asp Thursday, September 24, 2009

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for (var i=0; i < 5; i++) { // some code to run } Thursday, September 24, 2009

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for (var i=0; i < 5; i++) { // some code to run } before any loops Thursday, September 24, 2009

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for (var i=0; i < 5; i++) { // some code to run } before each loop Thursday, September 24, 2009

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for (var i=0; i < 5; i++) { // some code to run } after each loop Thursday, September 24, 2009

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for (var i=0; 0 < 5; i++) { // i would be 0 } Thursday, September 24, 2009

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for (var i=0; 1 < 5; i++) { // i would be 1 } Thursday, September 24, 2009

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for (var i=0; 2 < 5; i++) { // i would be 2 } Thursday, September 24, 2009

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for (var i=0; 3 < 5; i++) { // i would be 3 } Thursday, September 24, 2009

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for (var i=0; 4 < 5; i++) { // i would be 4 } Thursday, September 24, 2009

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for (var i=0; 5 < 5; i++) { // condition false so this // would never happen } Thursday, September 24, 2009

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for (var i=0; 5 < 5; i++) { // condition false so this // would never happen } Thursday, September 24, 2009

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var colors = ['red', 'green', 'blue']; for(var i=0; i < colors.length; i++) { colors[i]; } Thursday, September 24, 2009

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var colors = ['red', 'green', 'blue']; for(var i=0, length=colors.length; i < length; i++) { colors[i]; } Thursday, September 24, 2009

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var colors = ['red', 'green', 'blue']; var length = colors.length; for(var i=0; i < length; i++) { colors[i]; } Thursday, September 24, 2009

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while loop loop while a condition is true http://www.w3schools.com/JS/js_loop_while.asp Thursday, September 24, 2009

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var i = 0; while (i < 5) { // some code to run i++; } Thursday, September 24, 2009

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var i = 0; while (i < 5) { // some code to run i++; } before each loop Thursday, September 24, 2009

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var i = 0; while (0 < 5) { // i would be 0 i++; // i would be 1 } Thursday, September 24, 2009

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var i = 0; while (1 < 5) { // i would be 1 i++; // i would be 2 } Thursday, September 24, 2009

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var i = 0; while (2 < 5) { // i would be 2 i++; // i would be 3 } Thursday, September 24, 2009

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var i = 0; while (3 < 5) { // i would be 3 i++; // i would be 4 } Thursday, September 24, 2009

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var i = 0; while (4 < 5) { // i would be 4 i++; // i would be 5 } Thursday, September 24, 2009

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var i = 0; while (5 < 5) { // condition is false so // this would never happen i++; } Thursday, September 24, 2009

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var i = 0; while (5 < 5) { // condition is false so // this would never happen i++; } Thursday, September 24, 2009

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for..in loop loop through the properties of an object http://www.w3schools.com/jS/js_loop_for_in.asp Thursday, September 24, 2009

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for (property in object) { // some code here } Thursday, September 24, 2009

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var person = { name: 'John Nunemaker', age: 27, married: true, cat_owner: 'unfortunately' }; for (property in person) { property; person[property]; } Thursday, September 24, 2009

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var person = { name: 'John Nunemaker', age: 27, married: true, cat_owner: 'unfortunately' }; for (property in person) { property; // ‘name’ person[property]; // ‘John Nunemaker’ } Thursday, September 24, 2009

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var person = { name: 'John Nunemaker', age: 27, married: true, cat_owner: 'unfortunately' }; for (property in person) { property; // ‘age’ person[property]; // 27 } Thursday, September 24, 2009

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var person = { name: 'John Nunemaker', age: 27, married: true, cat_owner: 'unfortunately' }; for (property in person) { property; // ‘married’ person[property]; // true } Thursday, September 24, 2009

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var person = { name: 'John Nunemaker', age: 27, married: true, cat_owner: 'unfortunately' }; for (property in person) { property; // ‘cat_owner’ person[property]; // ‘unfortunately’ } Thursday, September 24, 2009

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break break the current loop and continue with code after loop if any http://www.w3schools.com/jS/js_break.asp Thursday, September 24, 2009

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think “stop looping right now” Thursday, September 24, 2009

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for (var i=0; i < 5; i++) { if (i === 2) { break; } i; } Thursday, September 24, 2009

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for (var i=0; 0 < 5; i++) { if (0 === 2) { // false break; } i; // 0 } Thursday, September 24, 2009

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for (var i=0; 0 < 5; i++) { if (0 === 2) { // false break; } i; // 0 } Thursday, September 24, 2009

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for (var i=0; 1 < 5; i++) { if (1 === 2) { // false break; } i; // 1 } Thursday, September 24, 2009

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for (var i=0; 1 < 5; i++) { if (1 === 2) { // false break; } i; // 1 } Thursday, September 24, 2009

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for (var i=0; 2 < 5; i++) { if (2 === 2) { // true break; // breaks out of loop } i; // never gets here } Thursday, September 24, 2009

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for (var i=0; 2 < 5; i++) { if (2 === 2) { // true break; // breaks out of loop } i; // never gets here } Thursday, September 24, 2009

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most common use is switch statement, but good to know it works elsewhere Thursday, September 24, 2009

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continue break the current loop and continue with the next value http://www.w3schools.com/jS/js_break.asp Thursday, September 24, 2009

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think “skip current loop” Thursday, September 24, 2009

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for (var i=0; i < 3; i++) { if (i === 1) { continue; } i; // comment } Thursday, September 24, 2009

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for (var i=0; 0 < 3; i++) { if (0 === 1) { // false continue; } i; // 0 } Thursday, September 24, 2009

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for (var i=0; 0 < 3; i++) { if (0 === 1) { // false continue; } i; // 0 } Thursday, September 24, 2009

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for (var i=0; 1 < 3; i++) { if (1 === 1) { // true continue; } i; // never gets here } Thursday, September 24, 2009

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for (var i=0; 1 < 3; i++) { if (1 === 1) { // true continue; } i; // never gets here } Thursday, September 24, 2009

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for (var i=0; 2 < 3; i++) { if (2 === 1) { // false continue; } i; // 2 } Thursday, September 24, 2009

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for (var i=0; 2 < 3; i++) { if (2 === 1) { // false continue; } i; // 2 } Thursday, September 24, 2009

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for (var i=0; 3 < 3; i++) { // never gets here if (i === 1) { continue; } i; } Thursday, September 24, 2009

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for (var i=0; 3 < 3; i++) { // never gets here if (i === 1) { continue; } i; } Thursday, September 24, 2009

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assignment04 http://teaching.johnnunemaker.com/capp-30550/sessions/looping/ Thursday, September 24, 2009