String 的扩展方法

let name = `zhangsan`;
​

let name = '张三'; 
let sayHello = `hello,my name is ${name}`; // hello, my name is zhangsan

 let result = { 
     name: 'zhangsan', 
     age: 20,
     sex: '男' 
 } 
 let html = ` <div>
     <span>${result.name}</span>
     <span>${result.age}</span>
     <span>${result.sex}</span>
 </div> `;
​

const sayHello = function () { 
    return '哈哈哈哈 追不到我吧 我就是这么强大';
 }; 
 let greet = `${sayHello()} 哈哈哈哈`;
 console.log(greet); // 哈哈哈哈 追不到我吧 我就是这么强大 哈哈哈哈
​

let str = 'Hello world!';
str.startsWith('Hello') // true 
str.endsWith('!')       // true
​

'x'.repeat(3)      // "xxx" 
'hello'.repeat(2)  // "hellohello"