on（）观察输入的变化(on() to watch changes in input)

on（）观察输入的变化(on() to watch changes in input) $("#myTextBox").on("change paste keyup", function() { alert($(this).val()); });

如何比较用户插入的新值和输入中已存在的当前值？

$("#myTextBox").on("change paste keyup", function() { alert($(this).val()); });

How can I compare the new value inserted by the user and the current value that already existed in the input?

最满意答案

奇怪的是，输入的value属性在其值更改时实际上并未更新。 因此，您可以简单地将.val()与attr("value")并在进行更改后更新attr("value") ：

例如：

$("#myTextBox").on("change paste keyup", function() {
   alert($(this).attr("value")+" vs "+$(this).val());
   $(this).attr("value",$(this).val());
}); 
  
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input id="myTextBox" value="abc" /> 
  
 
Weirdly, the input's value attribute is not actually updated when its value is changed. Therefore you can simply compare the .val() to the attr("value") and update the attr("value") after a change is made:
 
E.G:
 
 
 
  
  
$("#myTextBox").on("change paste keyup", function() {
   alert($(this).attr("value")+" vs "+$(this).val());
   $(this).attr("value",$(this).val());
}); 
  
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input id="myTextBox" value="abc" />