请问下为什么没替换成功？

打印信息为：
name
/${name}/ 'xiaoming'
the age of ${name} is ${age}
age
/${age}/ 8
the age of ${name} is ${age}

const template = "the age of ${name} is ${age}";
const data = { name: "xiaoming", age: 8};
console.log(render(template, data));
// 输出: "the age of xiaoming is 8"

function render(template,data) {
  for (key in data) {
    if(key) {
      console.log(key);
      var re = new RegExp("\$\{"+key+"\}");
      console.log(re,data[key]);
      var ans = template.replace(re,data[key]);
      // console.log("test:",template.replace("${name}","xiaoming"));
      console.log(ans); 
    }
    
  }
}