字符串模板
//植入变量
let obj = {
name : 'yk',
age : 12
}
let str = `我叫:${obj.name},年龄:${obj.age}`
console.log(str) //我叫:yk,年龄:12
//任意换行
let str2 = `<div>
<p>hello</p>
</div>`
console.log(str2)
//<div><p>hello</p></div>
startsWith endsWith
if(str.startsWith('181')){
return '电信'
}