javascript基础语法

一，变量类型(string/boolean/number/null/undefined)

val_i=23
val_i=1e3	(1000)
val_i=010	(八进制)
val_i=0xff	(十六进制)

val_s="Hello World"
val_b=true

typeof val_i

var b;
b === undefined; // true
b === "undefined"; // false
typeof b === "undefined"; // true
typeof b === undefined; // false

//字符串转数字
parseInt("123")

二，数组

//Array
var arr = [1, "yes", false, null, undefined, [1,2,3]]

arr.length //6
typeof arr //object
arr[0] ~ arr[arr.length - 1]

val_arr = arr.pop()	// val_arr = [1,2,3]
arr.push([1,2,3])
arr.push("new item")

//Associate Array
arr_a = {"name":"ciaos",'age':26}

typeof arr_a //object
arr_a["name"]//"ciaos"
arr_a.name	//"ciaos"
//遍历方式
for (var key in arr_a) {out+=key+":"+arr_a[key]+"¥n"}

if("name" in arr_a)
if(arr_a["name"])
if(arr_a.name)

三，流程控制语句

//While | For | Do While
i = 1;
sum = 0;
while (i <= 100) {
	sum += i++;
}

for (i = 1, sum = 0; i <= 100; i++) {
	sum += i;
}

do {
	sum += i++;
} while (i <= 100);

//Switch
var a = "";
var result = "";

switch (a) {
case false:
	result = "a is false";
	break;
case a + "hello": // Expressions are allowed here
	result = "what?";
	break;
case "": // Strict comparison
	result = "a is an empty string";
	break;
default:
	result = "@#$";
}

//Try Catch Finally
var msg = "";
try {
	throw new Error("ouch");
} catch (e) {
	msg += e.message;
} finally {
	msg += " - finally";
}
msg; // "ouch - finally"

四，函数

function funName(a,b){}

function sum(/* nothing here */) {
	for (var i = 0, result = 0; i < arguments.length; i++) {
		result += arguments[i];
	}
	return result;
}
sum(); // 0
sum(111); // 111
sum(1, 2); // 3
sum(1, 2, 3); // 6
sum(1, 10, 2, 9, 3, 8); // 33

//
var sum_t = sum
sum_t(1)

var immediate_one = function () {
	return 1;
}();
immediate_one	//	1
var immediate_one = function () {
	return 1;
};
immediate_one()	//	1

//闭包
function declare() {}
var express = function () {};
(function () {
	// Local scope
	function declare() {} // Declared and given a value
		var express = undefined; // Declared here
		console.log(typeof declare); // "function"
		console.log(typeof express); // "undefined"
		express = function () {}; // Implemented here
		console.log(typeof declare); // "function"
		console.log(typeof express); // "function"
}());

五，面向对象

//
function Dog() {
	this.name = "Fido";
	this.sayName = function () {
		return "Woof! " + this.name;
	};
	// 默认返回 return this;
}
var fido = new Dog();
fido.sayName(); // "Woof! Fido"

function Dog() {
	var notthis = {
		noname: "Anonymous"
	};
	this.name = "Fido";
	return notthis;
}
var fido = new Dog();
fido.name; // undefined
fido.noname; // "Anonymous"

function Dog() {
this.name = "Fido";
return 1;
}
var fido = new Dog();
typeof fido; // "object"
fido.name; // "Fido"
var one = Dog();
one;		// 1

//使用sayName添加成员函数
Dog.prototype.sayName = function () {
	return this.name;
};

 六，其它

JSON.stringify({hello: "world"}); // '{"hello":"world"}'
JSON.parse('{"hello":"world"}').hello; // "world"