onchange 属性在 javascript 中不起作用
[英]onchange property doesn`t work in javascript
问题描述
I want to launch the function test() if the user inputs something in the html input field with the id="sc1dc1" (without using the "onchange=" directly in HTML).
如果用户在id="sc1dc1"的 html 输入字段中输入某些内容（不直接在 HTML 中使用"onchange=" test()我想启动函数test() )。 What is wrong?怎么了？
HTML: HTML：
<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<body>
<input type="text" id="sc1dc1" >
</body>
</html>
Javascript: Javascript：
var x = document.getElementById("sc1dc1").value;
x.onchange = test;
function test(){alert("Test")};
3 个解决方案
解决方案1
1 已采纳 2018-12-27 23:08:58
The thing about onchange events is that they only fire when the <input> field loses focus.关于onchange事件的事情是它们只在<input>字段失去焦点时触发。 If you want an immediate response, you should use oninput like so:如果您想要立即响应，您应该像这样使用oninput ：
x.oninput = test;
You also need to make x equal to the actual element , not the value of the element.您还需要使x等于实际元素，而不是元素的值。 Removing:删除：
.value
From this line:从这一行：
var x = document.getElementById("sc1dc1").value;
Will fix it.会修好。
Demonstration with onchange :使用onchange演示：
var x = document.getElementById("sc1dc1"); x.onchange = test; function test() { alert("Test") };
<!DOCTYPE html> <html> <head> <title></title> </head> <body> <input type="text" id="sc1dc1"> </body> </html>
Demonstration with oninput :使用oninput演示：
var x = document.getElementById("sc1dc1"); x.oninput = test; function test() { alert("Test") };
<!DOCTYPE html> <html> <head> <title></title> </head> <body> <input type="text" id="sc1dc1"> </body> </html>
解决方案2
0 2018-12-27 23:07:22
The javascript should be this: javascript应该是这样的：
var x = document.getElementById("sc1dc1"); x.onchange = test; function test(){alert("Test")};
<!DOCTYPE html> <html> <head> <title></title> </head> <body> <input type="text" id="sc1dc1" > </body> </html>
You don't need .value你不需要 .value
解决方案3
0 2018-12-27 23:07:56
You need to assign the function test to the element's oninput attribute.您需要将功能test分配给元素的oninput属性。 x should be the HTMLInputElement , not the value of the element. x应该是HTMLInputElement ，而不是元素的值。
Change改变
var x = document.getElementById("sc1dc1").value;
To到
var x = document.getElementById("sc1dc1");
Use oninput instead of onchange if you want to trigger your event handler right when text is entered and not after the input loses focus.如果您想在输入文本oninput不是在输入失去焦点后立即触发事件处理程序，请使用oninput而不是onchange 。
var x = document.getElementById("sc1dc1"); x.oninput = test; function test(){alert("Test")};
<!DOCTYPE html> <html> <head> <title></title> </head> <body> <input type="text" id="sc1dc1" > </body> </html>
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