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1. JavaScript介紹

• JavaScript是一門廣泛用于瀏覽器客戶端的腳本語言

  • 腳本語言: 縮短傳統(tǒng)的編寫-編譯-鏈接-運行過程,解釋運行而非編譯運行

• JavaScriptl的常見用途

  • HTML DOM操作（節(jié)點操作，比如添加、修改、刪除節(jié)點）
  • 給HTML網(wǎng)頁增加動態(tài)功能，比如動畫
  • 事件處理：比如監(jiān)聽鼠標(biāo)點擊、鼠標(biāo)滑動、鍵盤輸入

2. JavaScript的編寫輸出形式

用js寫一個helloWord

alert("hello world")

利于調(diào)試,供程序員觀看：

console.log('hello world')

3. JavaScript的基本語法

• 數(shù)據(jù)類型
• 最值
• 函數(shù)
• 對象
• 邏輯字

(1)-------------JS中常見的數(shù)據(jù)類型----------

• js中定義變量必須用var

var age = 18;//number
var money = 1.099;//number
var name = 'wpf';
var result = false;// boolean
var score = null;//object
  // typeof 用于判斷變量的真實類型
 console.log(age, money, name, result, score);
console.log(typeof age, typeof money, typeof name, typeof result,typeof score);

(2)字符串的拼接

• 規(guī)律: 運算是從左往右,任何類型的變量與string類型拼接都會被轉(zhuǎn)為string

var str = 10 + 10 + '10' + '10';// 201010
var str1 = '10' + 10 + '10' + 10;//10101010
var str2 = ('10' + 10) + '10' + 10;//10101010
var str3 = '10' + '10' + 10 + 10;//10101010

(3)-----------------數(shù)組------------------

• 數(shù)組中可以放任意類型的數(shù)據(jù)

  var newArray = [10, -5, age, name, result, score, ['哈哈哈', 'abc', '123']];        //數(shù)組的類型 object
// 遍歷數(shù)組 方法1
      for (var  i = 0; i < newArray.length; i++){
     console.log(newArray[i]);
   }
// 遍歷數(shù)組2
for (var i in newArray) {
  console.log(i, newArray[i]);
  }
 console.log(newArray[newArray.length - 1][0]);//哈哈哈
// 刪除最后一個元素,添加一個新的元素到數(shù)組中 pop()和push()        newArray.pop();
 newArray.push(['大熊貓']);
 console.log(newArray);
 console.log(newArray[newArray.length - 1]);//['大熊貓']

(4)------------取出數(shù)組中的最大值和最小值-----------

• 方法1

var newNumbers = [10,3,23,938];
var minNumber = Math.min.apply(null,newNumbers);
var maxNumber = Math.max.apply(null,newNumbers);
console.log(minNumber, maxNumber);

• 方法2

var minNumber = Math.min(10,32,34,4554,-9);
var maxNumber = Math.max(10,32,34,4554,-9);
console.log(minNumber, maxNumber);

（5）函數(shù)
*函數(shù)的定義格式

 function 函數(shù)名（參數(shù)列表）{
        // 函數(shù)體

        函數(shù)沒有返回類型
    }

• 加法運算

// 兩個數(shù)相加
function sum(num1, num2){ // 參數(shù)列表不需要標(biāo)明類型
  return num1 + num2;
}
// 調(diào)用函數(shù)
var result = sum(245, 89);
console.log(result);


// 萬能的加法函數(shù)
function sum1(numbers){
   var count = 0;
  for (var i = 0; i < numbers.length; i++){
       count += numbers[i];
 }
  return count;
}
var  numbers = [12,124,'23'];
var result1 = sum1(numbers);
console.log(result1);


// 內(nèi)置數(shù)組 arguments
function sum2(){
 var count = 0;
  for(var i = 0; i < arguments.length; i++){
     count += arguments[i];
 }
  return count;
}
var result2 = sum2(90,23,45,67,87,34);
console.log(result2);

（6）對象

• this在哪個對象中,就代表該對象

1.單一對象

var peapole = {
name:'jack',
age:18,
height:178,
 friends:['rose','dog'],
eat:function (someThing){
   console.log(this.name + '------吃肉'+ someThing);
  },
 run:function (someWhere){
  console.log(this.name + '------跑' + someWhere);
  }};
// 調(diào)用對象的屬性
console.log(peapole.name, peapole.friends);
// 調(diào)用對象的方法
people.eat('肉');
people.run('船上');

2.批量產(chǎn)生對象

方法1.

//構(gòu)造函數(shù)
function Dog(){
  this.name = null;
  this.height = null;
  this.age = null;
  this.friends = [];
  this.eat = function (someThing){
     console.log(this.name + '------吃肉'+ someThing);
  };
  this.run = function (someWhere){
    console.log(this.name + '------跑' + someWhere);
  }
}
// 批量產(chǎn)生狗
var dog1 = new Dog();
var dog2 = new Dog();

// 賦值
dog1.name = 'huahua';
dog1.height = 1.33;
dog1.age = 8;
dog1.friends = ['lili','xixi'];

dog2.name = 'xniba';
dog2.height = 0.33;
dog2.age = 1;
dog2.friends = ['niuniu','lele'];
dog1.eat('meat');
dog2.eat('niunai');
console.log(dog1,dog2);

方法2

// 構(gòu)造函數(shù)
   function Dog(name, height, age, friends){
    this.name = name;
    this.height = height;
    this.age = age;
    this.friends = friends;
   this.eat = function(someThing){
       console.log(this.name + '吃' + someThing);
     },
      this.run = function(someWhere){
       console.log(this.name + '跑' + someWhere);
   }
  }
// 創(chuàng)建新的對象
  var  dog3 = new  Dog('nini',12,1,['haha','xixi']);
  console.log(dog3);

（7）邏輯關(guān)鍵字的運用

1.|| 邏輯或

var name1 = 'null';
var name2 = 'name2';
var name3 = 'name3';
var name4 = 'name4';
var newName = null;
// 判斷
if (name1){
  newName = name1;
} else if (name2){
  newName = name2;
} else if (name3){
  newName = name3;
} else {    newName = name4;
}
// 新的做法
newName = name1 || name2 || name3 || name4;
console.log(newName);

2.&& 邏輯與

var age = 22;
if (age>20){    console.log('大學(xué)畢業(yè)');}
(age > 20) && console.log('大學(xué)畢業(yè)');