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Conditional statements in JavaScript (if, if...else, if...else if...else, and switch).
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Conditionalsforks in the road
Tuesday, September 22, 2009
Tuesday, September 22, 2009
Tuesday, September 22, 2009
Tuesday, September 22, 2009
if statementexecute some code only if a statement is true
http://www.w3schools.com/JS/js_if_else.asp
Tuesday, September 22, 2009
if
Tuesday, September 22, 2009
if (conditional)
Tuesday, September 22, 2009
if (conditional) {
Tuesday, September 22, 2009
if (conditional) { // statement to be executed
Tuesday, September 22, 2009
if (conditional) { // statement to be executed}
Tuesday, September 22, 2009
truefalse
Tuesday, September 22, 2009
var age = 60;var status = null;
if (age > 62) { status = 'retired';}
status; // null
Tuesday, September 22, 2009
var age = 60;var status = null;
if (age > 62) { status = 'retired';}
status; // null
60 > 62 === false
this never executes
so status is never assigned and remains null
Tuesday, September 22, 2009
var age = 65;var status = null;
if (age > 62) { status = 'retired';}
status; // "retired"
Tuesday, September 22, 2009
var age = 65;var status = null;
if (age > 62) { status = 'retired';}
status; // "retired"
65 > 62 === true
this executes
so status is set to “retired”
Tuesday, September 22, 2009
if...else statementexecute some code if statement is true
and some other code if statement is falsehttp://www.w3schools.com/JS/js_if_else.asp
Tuesday, September 22, 2009
if (conditional) { // statement if true}
Tuesday, September 22, 2009
if (conditional) { // statement if true} else
Tuesday, September 22, 2009
if (conditional) { // statement if true} else {
Tuesday, September 22, 2009
if (conditional) { // statement if true} else { // statement if false
Tuesday, September 22, 2009
if (conditional) { // statement if true} else { // statement if false}
Tuesday, September 22, 2009
truefalse
Tuesday, September 22, 2009
var age = 60;var status = null;
if (age > 62) { status = 'retired';} else { status = 'not retired';}
status; // "not retired"
Tuesday, September 22, 2009
var age = 65;var status = null;
if (age > 62) { status = 'retired';} else { status = 'not retired';}
status; // "retired"
Tuesday, September 22, 2009
if...else if...else statementexecute some code if statement is true
and some other code if statement is falsehttp://www.w3schools.com/JS/js_if_else.asp
Tuesday, September 22, 2009
if (conditional) { // statement if true} else if (conditional) { // statement if false and else if true} else { // statement if all false}
Tuesday, September 22, 2009
if (conditional) { // statement if true} else if (conditional) { // whichever matches first} else if (conditional) { // whichever matches first} else if (conditional) { // whichever matches first} else { // statement if all false}
Tuesday, September 22, 2009
var age = 19;var status = null;
if (age >= 62) { status = 'retired';} else if (age > 22 && age < 62) { status = 'working';} else if (age >= 18 && age <= 22) { status = 'college';} else { status = 'no responsibilities';}
status;
Tuesday, September 22, 2009
switch statementselect one of many blocks of code to execute
http://www.w3schools.com/JS/js_switch.asp
Tuesday, September 22, 2009
switch
Tuesday, September 22, 2009
switch (value)
Tuesday, September 22, 2009
switch (value) {
Tuesday, September 22, 2009
switch (value) { case 1:
Tuesday, September 22, 2009
switch (value) { case 1: // some code to execute
Tuesday, September 22, 2009
switch (value) { case 1: // some code to execute break;
Tuesday, September 22, 2009
switch (value) { case 1: // some code to execute break; case 2: // some code to execute break;
Tuesday, September 22, 2009
switch (value) { case 1: // some code to execute break; case 2: // some code to execute break; default: // nothing matched so do this
Tuesday, September 22, 2009
switch (value) { case 1: // some code to execute break; case 2: // some code to execute break; default: // nothing matched so do this
similar to else in if...else
Tuesday, September 22, 2009
switch (value) { case 1: // some code to execute break; case 2: // some code to execute break; default: // nothing matched so do this}
Tuesday, September 22, 2009
var age = 18;
switch (typeof(age)) { case 'number': "I'm a number!"; break; case 'string': "I'm a string!"; break; case 'boolean': "I'm a boolean!"; break; default: "I don't know what I am!";}
// "I'm a number!"Tuesday, September 22, 2009
for(action in json) { var selectors = json[action]; switch(action) { case 'replace' : for(selector in selectors) $(selector).html(selectors[selector]); break; case 'append' : for(selector in selectors) $(selector).append(selectors[selector]); break; case 'prepend' : for(selector in selectors) $(selector).prepend(selectors[selector]); break; case 'replaceWith' : for(selector in selectors) $(selector).replaceWith(selectors[selector]); break; case 'insertBefore' : for(selector in selectors) $(selectors[selector]).insertBefore($(selector)); break; case 'sidebar' : Sidebar.add(selectors); break; case 'remove' : $(selectors.join(',')).remove(); break; }}
Tuesday, September 22, 2009
Review
Tuesday, September 22, 2009
var age = 18;var teens = false;
if (age > 12 && age < 20) { teens = true;}
teens;
Tuesday, September 22, 2009
var age = 18;var teens = false;
if (age > 12 && age < 20) { teens = true;}
teens; // true
Tuesday, September 22, 2009
var days = ['sunday', 'monday', 'tuesday'];var first = days[0];var week_starts_on_sunday = false;
if (first === 'sunday') { week_starts_on_sunday = true;}
week_starts_on_sunday;
Tuesday, September 22, 2009
var days = ['sunday', 'monday', 'tuesday'];var first = days[0];var week_starts_on_sunday = false;
if (first === 'sunday') { week_starts_on_sunday = true;}
week_starts_on_sunday; // true
Tuesday, September 22, 2009
var days = ['monday', 'tuesday', 'sunday'];var first = days[0];var week_starts_on_sunday = false;
if (first === 'sunday') { week_starts_on_sunday = true;}
week_starts_on_sunday;
Tuesday, September 22, 2009
var days = ['monday', 'tuesday', 'sunday'];var first = days[0];var week_starts_on_sunday = false;
if (first === 'sunday') { week_starts_on_sunday = true;}
week_starts_on_sunday; // false
Tuesday, September 22, 2009
Assignmenthttp://teaching.johnnunemaker.com/capp-30550/sessions/conditionals
Tuesday, September 22, 2009