diff options
Diffstat (limited to 'javascript.html.markdown')
| -rw-r--r-- | javascript.html.markdown | 60 |
1 files changed, 46 insertions, 14 deletions
diff --git a/javascript.html.markdown b/javascript.html.markdown index ba2e8ce4..a119be88 100644 --- a/javascript.html.markdown +++ b/javascript.html.markdown @@ -54,6 +54,11 @@ doStuff() // Including uneven division. 5 / 2; // = 2.5 +// And modulo division. +10 % 2; // = 0 +30 % 4; // = 2 +18.5 % 7; // = 4.5 + // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 @@ -64,7 +69,7 @@ doStuff() // There are three special not-a-real-number values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 -NaN; // result of e.g. 0/0 +NaN; // result of e.g. 0/0, stands for 'Not a Number' // There's also a boolean type. true; @@ -104,7 +109,7 @@ null == undefined; // = true // ...unless you use === "5" === 5; // = false -null === undefined; // = false +null === undefined; // = false // ...which can result in some weird behaviour... 13 + !0; // 14 @@ -144,6 +149,10 @@ someOtherVar = 10; // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined +// if you wan't to declare a couple of variables, then you could use a comma +// separator +var someFourthVar = 2, someFifthVar = 4; + // There's shorthand for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar is 10 now someVar *= 10; // now someVar is 100 @@ -189,7 +198,7 @@ myObj.myFourthKey; // = undefined /////////////////////////////////// // 3. Logic and Control Structures -// The syntax for this section is almost identical to Java's. +// The syntax for this section is almost identical to Java's. // The `if` structure works as you'd expect. var count = 1; @@ -218,6 +227,26 @@ for (var i = 0; i < 5; i++){ // will run 5 times } +//The For/In statement loops iterates over every property across the entire prototype chain +var description = ""; +var person = {fname:"Paul", lname:"Ken", age:18}; +for (var x in person){ + description += person[x] + " "; +} + +//If only want to consider properties attached to the object itself, +//and not its prototypes use hasOwnProperty() check +var description = ""; +var person = {fname:"Paul", lname:"Ken", age:18}; +for (var x in person){ + if (person.hasOwnProperty(x)){ + description += person[x] + " "; + } +} + +//for/in should not be used to iterate over an Array where the index order is important. +//There is no guarantee that for/in will return the indexes in any particular order + // && is logical and, || is logical or if (house.size == "big" && house.colour == "blue"){ house.contains = "bear"; @@ -231,8 +260,8 @@ var name = otherName || "default"; // The `switch` statement checks for equality with `===`. -// use 'break' after each case -// or the cases after the correct one will be executed too. +// use 'break' after each case +// or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': @@ -262,12 +291,9 @@ myFunction("foo"); // = "FOO" // Note that the value to be returned must start on the same line as the // `return` keyword, otherwise you'll always return `undefined` due to // automatic semicolon insertion. Watch out for this when using Allman style. -function myFunction() -{ +function myFunction(){ return // <- semicolon automatically inserted here - { - thisIsAn: 'object literal' - } + {thisIsAn: 'object literal'} } myFunction(); // = undefined @@ -281,6 +307,12 @@ setTimeout(myFunction, 5000); // Note: setTimeout isn't part of the JS language, but is provided by browsers // and Node.js. +// Another function provided by browsers is setInterval +function myFunction(){ + // this code will be called every 5 seconds +} +setInterval(myFunction, 5000); + // Function objects don't even have to be declared with a name - you can write // an anonymous function definition directly into the arguments of another. setTimeout(function(){ @@ -299,7 +331,7 @@ i; // = 5 - not undefined as you'd expect in a block-scoped language // scope. (function(){ var temporary = 5; - // We can access the global scope by assiging to the "global object", which + // We can access the global scope by assigning to the "global object", which // in a web browser is always `window`. The global object may have a // different name in non-browser environments such as Node.js. window.permanent = 10; @@ -393,7 +425,7 @@ var doubler = product.bind(this, 2); doubler(8); // = 16 // When you call a function with the `new` keyword, a new object is created, and -// made available to the function via the this keyword. Functions designed to be +// made available to the function via the `this` keyword. Functions designed to be // called like that are called constructors. var MyConstructor = function(){ @@ -516,12 +548,12 @@ more about how to use JavaScript in web pages, start by learning about the [Document Object Model](https://developer.mozilla.org/en-US/docs/Using_the_W3C_DOM_Level_1_Core) -[Learn Javascript by Example and with Challenges](http://www.learneroo.com/modules/64/nodes/350) is a variant of this reference with built-in challenges. +[Learn Javascript by Example and with Challenges](http://www.learneroo.com/modules/64/nodes/350) is a variant of this reference with built-in challenges. [JavaScript Garden](http://bonsaiden.github.io/JavaScript-Garden/) is an in-depth guide of all the counter-intuitive parts of the language. -[JavaScript: The Definitive Guide](http://www.amazon.com/gp/product/0596805527/) is a classic guide / reference book. +[JavaScript: The Definitive Guide](http://www.amazon.com/gp/product/0596805527/) is a classic guide / reference book. In addition to direct contributors to this article, some content is adapted from Louie Dinh's Python tutorial on this site, and the [JS |