实时复制另一个文本框值Jquery

Question

我想获取另一个文本框的值并将其实时输入到另一个文本框中.如果TEXT_3改变了,我如何检测？如果TEXT_3值已更改,则必须输入TEXT_4为方便起见,以下是代码和演示:

**HTML**
    <label>TEXT 1: </label><input type="text" id="text_1" value=""/>
    <label>TEXT 2: </label><input type="text" id="text_2" value=""/>
    <label>TEXT 3: </label><input type="text" id="text_3" value=""/>
    <label>TEXT 4: </label><input type="text" id="text_4" value=""/>

**JAVASCRIPT**
    /* INPUT TEXT_1 AND TEXT_2 VALUE TO TEXT_3 ON TEXT_1 KEYUP*/
    $("#text_1").keyup(function() {
        $("#text_3").val($("#text_1").val() + " " + $("#text_2").val());
    })

    /* INPUT TEXT_1 AND TEXT_2 VALUE TO TEXT_3 ON TEXT_1 AND TEXT_2 KEYUP*/    
    $("#text_2").keyup(function(){
        $("#text_3").val($("#text_1").val() + " " + $("#text_2").val());
    })

    /* HOW CAN I  DETECT IF TEXT_3 WAS CHANGED? IF TEXT_3 VALUE CHANGED, IT MUST BE INPUTTED TO TEXT_4*/

    /* not working solution */   
    $("#text_3").change(function(){
        $("#text_4").val($("#text_3").val());
    })

演示:http://jsfiddle.net/8eXRx/7/

谢谢你的回复!

Answer 1

在textbox3.val()之后添加change(),如下所示:

$("#text_1").keyup(function() {
    $("#text_3").val($("#text_1").val() + " " + $("#text_2").val()).change();
})

/* INPUT TEXT_1 AND TEXT_2 VALUE TO TEXT_3 ON TEXT_1 AND TEXT_2 KEYUP*/    
$("#text_2").keyup(function(){
    $("#text_3").val($("#text_1").val() + " " + $("#text_2").val()).change();
})

http://jsfiddle.net/8eXRx/12/