一 实现模版字符串解析

var template = `
 <div>
 <% if(name){ %>
 <span>%= name =%</span>
 <% } %>
 %= age =%
 <div>`
 let str = rander(template, {name: '⼩明', age: 18})
 // 解析完成 str <div> <span>⼩明</span>18<div>