1.console.log用法，这个新手，比如我容易找不到console，细心点，在浏览器下方的选项卡里面，下面测试(ps:要用firebug)
<script> var me = 'Felix' console.log('hello word',me,",haha"); </script>
输出结果：hello word Felix ,haha
// Anything following double slashes is an English-language comment. // Read the comments carefully: they explain the JavaScript code. // variable is a symbolic name for a value. // Variables are declared with the var keyword: var x; // Declare a variable named x. // Values can be assigned to variables with an = sign x = 0; // Now the variable x has the value 0 x // => 0: A variable evaluates to its value. // JavaScript supports several types of values x = 1; // Numbers. x = 0.01; // Just one Number type for integers and reals. x = "hello world"; // Strings of text in quotation marks. x = 'JavaScript'; // Single quote marks also delimit strings. x = true; // Boolean values. x = false; // The other Boolean value. 4 | Chapter 1: Introduction to JavaScriptx = null; // Null is a special value that means "no value". x = undefined; // Undefined is like null.
需要注意的知识点：
1.用var定义变量，用等号赋值。
2.js支持的类型：整型，实数类型，文本字符串（可以用双引号或者单引号），布尔类型，无值类型(null/undefined)类型。
3.对象类型的属性、或者数组的元素都可以通过"."或者[""]访问。初始化object类型用={};如果{}里面无内容，表示空对象（没有属性的对象），但是可以用赋值的方法增加属性,如ob.newproperty = "test";
4.数组类型,初始化用=[1,2]的类似形式实现。定义和一般的类型相同，可以用primes.length获取数组的元素个数。访问最后一个元素是primes[primes.length-1]注意不要越界。
5.对象和数组可以存放其他对象和数组。
var points = [ // 存放两个对象 {x:0, y:0}, {x:1, y:1} ];
1 var data = { // 本对象有两个属性 2 trial1: [[1,2], [3,4]], // 每个对象的值都是数组 3 trial2: [[2,3], [4,5]] // 数组里面的元素还是一个数组 4 };
6.函数的定义和赋参数是用 function name(paras){}格式，函数可以赋值到变量。如下面代码：
1 var square = function(x) { // Functions are values and can be assigned to vars 2 return x*x; // Compute the function's value 3 }; // Semicolon marks the end of the assignment. 4 square(plus1(y)) // => 16: invoke two functions in one expression
7.当我们吧函数（function）结合到对象，我们叫他对象的“方法（method）”。
1 // When functions are assigned to the properties of an object, we call 2 // them "methods". All JavaScript objects have methods: 3 var a = []; // Create an empty array 4 a.push(1,2,3); // The push() method adds elements to an array 5 a.reverse(); // Another method: reverse the order of elements
8.我们可以定义自己的方法，用this关键字指向它所在的函数区域对应的变量。
points.dist = function() { // Define a method to compute distance between points var p1 = this[0]; // First element of array we're invoked on var p2 = this[1]; // Second element of the "this" object var a = p2.x-p1.x; // Difference in X coordinates var b = p2.y-p1.y; // Difference in Y coordinates return Math.sqrt(a*a + // The Pythagorean theorem b*b); // Math.sqrt() computes the square root }; points.dist() // => 1.414: distance between our 2 points
另一种用对象的实现
//定义一个构造函数，可以初始化一个point对象 function Point(x,y) { //按照惯例，构造函数以大写字母开始 this.x = x; //this 关键字指向新初始化的对象 this.y = y; // Store function arguments as object properties } // No return is necessary // Use a constructor function with the keyword "new" to create instances var p = new Point(1, 1); // The geometric point (1,1) // Define methods for Point objects by assigning them to the prototype // object associated with the constructor function. Point.prototype.r = function() { return Math.sqrt( // Return the square root of x² + y² this.x * this.x + // This is the Point object on which the method... this.y * this.y // ...is invoked. ); }; // Now the Point object p (and all future Point objects) inherits the method r() p.r() // => 1.414...