JavaScript Element.value 与 Element.getAttribute("value")

2022-01-13 00:00:00 attributes dom javascript html

我最近开始学习 JavaScript，但有些东西让我感到困惑:

I've started learning JavaScript recently but there's something that I'm confused with :

Element.value 和 Element.getAttribute("value") ?

实际上我的问题是，当我尝试将类型为 text 的 input 元素的值复制到另一个时，如果我使用第一种方法(Element.value) 它工作正常，但是如果我使用第二种方法它会复制给元素的第一个值，并且当我更改 textbox 内的文本时它永远不会更新，这种行为对我来说似乎很奇怪！你们能解释一下这里发生了什么吗?

actually my problem is , when I try to copy the value of an input element with type of text to another one , if I use the first method (Element.value) It works fine but if I go with the second method It copies the first value given to the element and It never gets updated when I change the text inside the textbox , this behavior seems odd to me ! can you guys please explain what's going on here ?

<html>
<head>
    <meta charset="utf-8">
    <title>Hello JavaScript</title>
    <script src="script2.js"></script>
</head>
<body>
    <input id="Text1" type="text" />
    <input id="Button1" type="button" value="button" />
    <input id="Text2" type="text" />
</body>
</html>

JavaScript 文件:

The JavaScript file :

var myButton;

window.onload = function () {

    myButton = document.getElementById("Button1");
    myButton.onclick = function () {
        var val = document.getElementById("Text1").getAttribute("value");  
        //var val = document.getElementById("Text1").value;
        document.getElementById("Text2").setAttribute("value", val);
    };

};

推荐答案

不同之处在于 element.value 是实时的，如果用户更改，比如说文本框输入，它将反映，并向您展示新值.

The difference is that element.value is real time and if a user changes let's say, a textbox input, it will reflect that, and show you the new value.

虽然 getAttribute('value') 仍会显示原始 value="whateverWasHere" 值.

While getAttribute('value') will still show the original value="whateverWasHere" value.

jsFiddle 演示

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