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Diffstat (limited to 'javascript.html.markdown')
| -rw-r--r-- | javascript.html.markdown | 45 |
1 files changed, 32 insertions, 13 deletions
diff --git a/javascript.html.markdown b/javascript.html.markdown index cce488e1..e285ca4e 100644 --- a/javascript.html.markdown +++ b/javascript.html.markdown @@ -16,9 +16,14 @@ JavaScript isn't just limited to web browsers, though: Node.js, a project that provides a standalone runtime for Google Chrome's V8 JavaScript engine, is becoming more and more popular. +JavaScript has a C-like syntax, so if you've used languages like C or Java, +a lot of the basic syntax will already be familiar. Despite this, and despite +the similarity in name, JavaScript's object model is significantly different to +Java's. + ```js -// Comments are like C's. Single-line comments start with two slashes, -/* and multiline comments start with slash-star +// Single-line comments start with two slashes. +/* Multiline comments start with slash-star, and end with star-slash */ // Statements can be terminated by ; @@ -36,7 +41,7 @@ doStuff() // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers -// up to about 9✕10¹⁵ precisely. +// up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 @@ -96,6 +101,10 @@ false; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" +// ... which works with more than just strings +"1, 2, " + 3; // = "1, 2, 3" +"Hello " + ["world", "!"] // = "Hello world,!" + // and are compared with < and > "a" < "b"; // = true @@ -136,7 +145,7 @@ undefined; // used to indicate a value is not currently present (although // character. var someVar = 5; -// if you leave the var keyword off, you won't get an error... +// If you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope @@ -145,7 +154,7 @@ 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 +// If you want to declare a couple of variables, then you could use a comma // separator var someFourthVar = 2, someFifthVar = 4; @@ -194,8 +203,6 @@ myObj.myFourthKey; // = undefined /////////////////////////////////// // 3. Logic and Control Structures -// The syntax for this section is almost identical to Java's. - // The `if` structure works as you'd expect. var count = 1; if (count == 3){ @@ -223,15 +230,15 @@ 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 +// The for/in statement 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 +// To only consider properties attached to the object itself +// and not its prototypes, use the `hasOwnProperty()` check. var description = ""; var person = {fname:"Paul", lname:"Ken", age:18}; for (var x in person){ @@ -240,8 +247,9 @@ for (var x in person){ } } -//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 +// For/in should not be used to iterate over an Array where the index order +// is important, as 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"){ @@ -256,7 +264,7 @@ var name = otherName || "default"; // The `switch` statement checks for equality with `===`. -// use 'break' after each case +// Use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { @@ -503,6 +511,10 @@ myNumber === myNumberObj; // = false if (0){ // This code won't execute, because 0 is falsy. } +if (new Number(0)){ + // This code will execute, because wrapped numbers are objects, and objects + // are always truthy. +} // However, the wrapper objects and the regular builtins share a prototype, so // you can actually add functionality to a string, for instance. @@ -547,6 +559,11 @@ of the language. [JavaScript: The Definitive Guide][6] is a classic guide and reference book. +[Eloquent Javascript][8] by Marijn Haverbeke is an excellent JS book/ebook with attached terminal + +[Javascript: The Right Way][9] is a guide intended to introduce new developers to JavaScript and help experienced developers learn more about its best practices. + + In addition to direct contributors to this article, some content is adapted from Louie Dinh's Python tutorial on this site, and the [JS Tutorial][7] on the Mozilla Developer Network. @@ -559,3 +576,5 @@ Mozilla Developer Network. [5]: http://bonsaiden.github.io/JavaScript-Garden/ [6]: http://www.amazon.com/gp/product/0596805527/ [7]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/A_re-introduction_to_JavaScript +[8]: http://eloquentjavascript.net/ +[9]: http://jstherightway.org/ |