ES6教程-字符串，函数的参数，了解函数的arguments对象，js面向对象，设计模式-单例模式，解构赋值

前言

主要讲解了ES6对字符串的拓展，包括includes，startsWith和endsWith，另外增加了字符串模板。

Start

includes()是否包含

startsWith()以什么开头

endsWith()以什么结尾

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-字符串</title>
</head>
<body>
 <script>
   let str = "你怎么一直在这";
   let res = str.includes('一');
   console.log(res);
 </script>
</body>
</html>

返回结果为true

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-字符串</title>
</head>
<body>
 <script>
   let str = "你怎么一直在这";
   let res = str.startsWith('你');
   console.log(res);
 </script>
</body>
</html>

返回结果为true

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-字符串</title>
</head>
<body>
 <script>
   let str = "你怎么一直在这";
   let res = str.startsWith('你');
   if(str.startsWith('你')){
     执行语句;
   }else if(语句){
     执行语句;
   }else{
     执行语句;
   }
 </script>
</body>
</html>

str.endsWith();

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-字符串</title>
</head>
<body>
 <script>
   let str = "你怎么一直在这";
   alert( str.endsWith('这'));
 </script>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-字符串</title>
</head>
<body>
 <script>
   let mail = '34234@qq.com';

   if( mail.endsWith('@qq.com') || main.endsWith('@163.com') ){
      alert('输入正确');
    }else{
      alert('请输入邮箱');
    }
 </script>
</body>
</html>

字符串模板

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-字符串</title>
</head>
<body>
 <script>
   let str2 = `
               <ul>
                 <li>内容</li>
               </ul>
               `;
    console.log(str2);
 </script>
</body>
</html>

函数的参数

函数的参数，展开运算符：...

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-函数参数</title>
</head>
<body>
 <script>
  function fun(a,b){
    console.log(a,b);
  }

  fun(1,2);
 </script>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-函数参数</title>
</head>
<body>
 <script>
  function fun(a,b,...args){
    console.log(a,b);
    console.log(...args);
  }
  fun(1,2,3,4,5);
  fun(1,2);
 </script>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-函数参数</title>
</head>
<body>
 <script>
  let arr = [1,2,3];
  function fun(a,b,c){
   console.log(a);
   console.log(b);
   console.log(c);
  }
  fun(arr[0],arr[1],arr[2]);
  fun(...arr);
 </script>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-函数参数</title>
</head>
<body>
 <script>
  let arr = [1,2,3];
  let arr1=[4,5,6];
  let array=[...arr,...arr1];
  console.log(array);
 </script>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>ES6-函数参数</title>
</head>
<body>
 <script>
  function fun(a=1,b=2,c=3){
   console.log(a,b,c);
  }
  fun();
  // fun(4,5,6);
 </script>
</body>
</html>

了解函数的arguments对象

arguments为一个对象，类数组

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>Document</title>
</head>
<body>
 <script>
   function add(a,b){
    return a+b;
   }
   console.log(add(1,2);
 </script>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <title>Document</title>
</head>
<body>
 <script>
   function add(){
    // console.log( arguments); // 返回对象
    return arguments[0] + arguments[1];
   }
   add(1,2);
   console.log( add(1,2) );
 </script>
</body>
</html>

js面向对象

// var student = {}; //创建对象
var student = new Object();
student.name = "dashu";
student.age = 12;
student.job = "school student";
student.study = function(){
 alert("study");
}
student.study();

var student = {
 name : "dashu",
 age : 12;
 job: "school student",
 study : function(){
  alert("study");
  }
};
student.study();

数据属性js中的

var student = {
 name: "dashucoding"
}
alert(student.name);

var student={};
Object.defineProperty(student,"name",{
 writable:true,
 value: "dashucoding"
});
alert(student.name);

configurable表示能否通过delete来删除属性值，默认为true

Enumerable表示能否通过for-in来枚举对象的属性值，默认为true

writable表示能否修改属性值，默认为true

设计模式-单例模式

var mask = function(){
 document.body.appendChild(document.createElement('div'));
}
var obtn = document.getElemetnById("btn");
obtn.onclick = function(){
 mask();
}

// 单例模式
var singleton = function(){
 var res;
 return function(fn){
  return res||(res=fn.apply(this,arguments))
 }
}();
var obtn = document.getElementById("btn");
obtn.onclick=function(){
 singleton(function(){
  return document.body.appendChild(document.createEelement('div'));
 })
}

解构赋值

解构赋值为一种表达式，用来获取数据

let arr=[1,2,3];
let a = arr[0];
let b = arr[1];
let c = arr[2];
console.log(a,b,c);

let arr = [1,2,3];
let [a,b,c] = arr;
console.log(a,b,c);

let arr = {
 a:1,
 b:2,
 c:3
}
let (a,b,c) = arr;
// let(a,b,c) = [1,2,3];
console(a,b,c);

结语

• 本文主要讲解 ES6教程-字符串，函数的参数，了解函数的arguments对象，js面向对象，设计模式-单例模式，解构赋值
• 下面我将继续对其他知识 深入讲解 ，有兴趣可以继续关注
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