JavaScript笔记

01-JS的常用语法

两种输出方式

1,弹框输出

alert('hello world');
alert('还是 hello world'); 
//上面这两句会先后弹出提示框,而不是只弹出第二句

2,调试输出

console.log('你好...呵呵..');

注意:结尾是分号(;) , 括号里写单引号' '

基本数据类型的运算:

1.运算时从左往右
2.任何类型的变量与String运算 , 都会被转为String类型/拼接字符串,万物皆对象!!

//1.基本的数据类型
var age = 10;//同swift
var height = 165.5;
var name = 'Jack';    name2 = 'Rose';
var result = true;//false
var score = null;

1.1制定类型遍历

var carName = String();//这是String类型        
var carName = new String;//这是对象类型Object类型

2.字符串的拼接

var newName = name + '和' + name2;
console.log(newName);
输出:Jack和Rose

3.练习

var str1 = 10 + 10 + '10';//2010
var str2 = '10' + 10 + 10;//101010
var str3 = (10 + '10') + 10;//101010
var str4 = '10' + (10 + 10);//1020
var str5 = '10'+ (10 + 10 + '10');//102010
console.log(str1,str2,str3,str4,str5);

4.数组

var arr = [];
arr.push(20,10.5,'hehe',['小伟子','18']);
console.log(arr);

输出:Array[4]
        0: 20
        1: 10.5
        2: "hehe"
        3: Array[2]
        length: 4

遍历数组
//swift3.0废弃了for(;;)这种遍历
for(var i = 0;i

02-JS中的函数

01-JS的常用语法

1.加法

function sum(num1,num2){
    return num1 + num2;
}
var result = sum(10,20);
console.log(result);
输出30

2.万能加法

function sum2(numbers){
    //变量
    var result = 0;
    for (var i in numbers){
        result += numbers[i];
    }   
    //返回
    return result;
}
var result1 = sum2([10,20,30]);
console.log(result1);//输出60

3.匿名函数

var res = function(){
     console.log('我是匿名函数');
 };
//调用
res();
//输出:我是匿名函数

4.JS中函数作为参数

function test1(num1){
    return num1;
}
console.log(sum(test1(10),10));

5.JS中的闭包!

function test2(num1){
    return function(num2){
        return num1+num2;    
    }
}
var temp = test2(4);
var temp2 = temp(5);//因为闭包!
console.log(temp2);//打印9

6.JS中的作用域

//流程控制语句内部不会有单独的作用域      
//说明函数(方法内部有单独的作用域)       
var temp3 = 'oldTemp';
//        if(true){
//            var temp3 = 'newTemp';
//        }        
function test(){
    var temp3 = 'newTemp';
}        
test();
console.log(temp3 == 'newTemp');

7.JS中没有类的概念,只有对象

var obj = new Object();
obj.name = 'jake';
obj.click = function(){
    alert('我被点击了');
};
//创建对象
var obj1 = {
    name : 'jake',
    click : function(){
    alert('我被点击了');
}

03-JS中创建对象

1.创建对象

var dog = {
    name:'旺财',
    age:18,
    height:1.55,
    dogFriends:['小花','xiaowang'],
    eat:function (someThing) {
        //this:this所在的函数属于哪一个对象,this就代表哪个对象
        console.log('吃' + this.name + someThing);
    },
    run:function (someWhere) { 
        console.log('跑' + this.name + someWhere);
    }
};

2.输出对象的属性和行为

console.log(dog.name,dog.age);
dog.eat('五花肉');
dog.run('操场');

03-JS中构造函数

1.创建构造函数--->抽象

var Dog = function (){
    this.name = null;
    this.age = null;
    this.dogFriends = [];
    this.height = null;
    this.eat = function (someThing){
        console.log(this.name + '吃' + someThing)
    };
    this.run = function (someWhere){
        console.log(this.name + '跑' + someWhere)
    };
};

2.创建带参数的构造函数

var Dog1 = function (name,age,dogFriends,height){
    this.name = name;
    this.age = age;
    this.dogFriends = dogFriends;
    this.height = height;
    this.eat = function (someThing){
        console.log(this.name + '吃' + someThing)
    };
    this.run = function (someWhere){
        console.log(this.name + '跑' + someWhere)
    };
};

3.普通函数调用

Dog();
//alloc init ----->new
var dog1 = new Dog();
dog1.name = 'ahuang';
dog1.age = 16;
dog1.dogFriends = ['abc','def'];
var dog2 = new Dog();
dog2.name = 'aasd';
dog2.age = 15;
dog2.dogFriends = ['abc11','def11'];
console.log(dog1,dog2);

输出

图片.png