Javascript 为什么在尝试将元素附加到文档时出错？

我有自定义方法：

prependCities() {
  if(process.client) {
    var locations = document.createElement("datalist");
    locations.id = "locations";
    var cities = this.cities;
    for(var i = 0; i < cities.length; i++) {
        var opt = cities[i];
        var el = document.createElement("option");
        el.textContent = opt;
        el.value = opt;
        locations.appendChild(el);
    }​
    var body = document.getElementsByTagName("form")[0]; 
    body.insertBefore(locations, body.children[0]);
  }
}

---

哪里有错误？

此列中有一个不可见字符

请看这里：

---

此列中有一个不可见的字符

请看这里：

这对我有用。看一看:

这对我有用。看一看:

  418 |             el.value = opt;
  419 |             locations.appendChild(el);
> 420 |         }​
      |          ^
  421 |         var body = document.getElementsByTagName("form")[0]; 
  422 |         body.insertBefore(locations, body.children[0]);
  423 |       }

prependCities() {
  if(process.client) {
    var locations = document.createElement("datalist");
    locations.id = "locations";
    var cities = this.cities;
    for(var i = 0; i < cities.length; i++) {
        var opt = cities[i];
        var el = document.createElement("option");
        el.textContent = opt;
        el.value = opt;
        locations.appendChild(el);
    }
    var body = document.getElementsByTagName("form")[0]; 
    body.insertBefore(locations, body.children[0]);
  }
}

prependCities() {
  if(process.client) {
    var locations = document.createElement("datalist");
    locations.id = "locations";
    var cities = this.cities;
    for(var i = 0; i < cities.length; i++) {
        var opt = cities[i];
        var el = document.createElement("option");
        el.textContent = opt;
        el.value = opt;
        locations.appendChild(el);
    }
    var body = document.getElementsByTagName("form")[0]; 
    body.insertBefore(locations, body.children[0]);
  }
}