獲取「event.target.id」作爲字符串

Question

下面的腳本返回一個錯誤：

"Uncaught TypeError: Object Reg_8712 has no method 'indexof' 

Reg_8712是單選按鈕ID是誰開的事件。

腳本：

$("input:radio").change(function (event) {    

      alert(event.target.id); // this works! it returns it as string. 
      var eti = event.target.id; // 'eti' gets the object and not the string. 
      var n = eti.indexof("_"); // error! cannot indexof ('eti' is an object and not string) 
      var fid = eti.substring(n); 

我怎樣才能獲得 'ETI' 作爲字符串？

Answer 1

語法indexOf

string.indexOf(searchValue[, fromIndex])

 alert(event.target.id); // this works! it returns it as string. 
     var eti = event.target.id.toString(); // 'eti' gets the object and not the string. 
     var n = eti.indexOf("_"); // error! cannot indexof ('eti' is an object and not string) 
     var fid = eti.substring(n); 

編號：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf

Answer 2

萬一出的確不是一個字符串，最簡單的方式轉換爲使用泛型.toString()方法：

var eti = event.target.id.toString(); 
var n = eti.indexOf("_"); 

Simple test case來證明這一點。