变更事件的jQuery没有开火

Question

该事件因某种原因没有触发

<div id="plotSelectionBar">
    <span>Select What to plot</span>
    <select class="plotSelector" id="firstDropdown">
        <option value="A">A</option>
        <option value="B">B</option>
        <option value="C">C</option>                
    </select>
    <span>Select What to plot2</span>
    <select class="plotSelector" id="secondDropdown">
        <option value="A">A</option>
        <option value="B">B</option>
        <option value="C">C</option>                
    </select>
 </div>

事件句柄如下：

$('.plotSelector').change(function(e)
{ if (this.id="firstDropdown)
  {
  //do something
  }
  else {//do something}
});

我在此上方有另一个事件手柄，该事件正好很好。发生了什么事？

Answer 1

您有语法错误，需要准备好调用文档，之后仅使用您的元素更改事件

$( document ).ready(function() {
  $('.plotSelector').change(function(e){
      if(this.id == "firstDropdown")
        alert(1)
        else
        {
          alert(2)
        }
  })
  
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<div id="plotSelectionBar">
    <span>Select What to plot</span>
    <select class="plotSelector" id="firstDropdown">
        <option value="A">A</option>
        <option value="B">B</option>
        <option value="C">C</option>                
    </select>
    <span>Select What to plot2</span>
    <select class="plotSelector" id="secondDropdown">
        <option value="A">A</option>
        <option value="B">B</option>
        <option value="C">C</option>                
    </select>
 </div>