JavaScript:onchange 函数导致错误/不起作用 [英] JavaScript : onchange function causes error/ didn't work

问题描述

以下代码将添加文件上传和预览字段.

<b>这个单一的 img 有效，但在 js 中无效</b><br><img id="img" alt="你的图片" width="100" height="100"/><input type="file" onchange="document.getElementById('img').src = window.URL.createObjectURL(this.files[0])"><br/>没有 Img <input type="text" id="noi" name="noi" value="" onkeyup="addFields()"><br/><脚本>函数 addFields(){//要创建的输入数var number = document.getElementById("noi").value;//容器 
将放置动态内容的位置var container = document.getElementById("container");var array = ["CRICTICAL","HIGH","LOW","INFO"];//清除容器之前的内容而 (container.hasChildNodes()) {container.removeChild(container.lastChild);}for (i=1;i<=number;i++){var img = document.createElement("img");img.width="100";img.height="100";img.id="img"+i;var upload = document.createElement("输入");上传类型=文件"；//这部分不工作_______________upload.onchange="document.getElementById(img.id).src = window.URL.createObjectURL(this.files[0])";//________________________________________container.appendChild(img);container.appendChild(上传);container.appendChild(document.createElement("br"));}}<div id="容器"/>

问题:

如果没有 Container appendChild 函数，代码运行良好，您可以在前三行代码中看到.

解决方案

你必须在 upload.onchange 中运行一个函数.像这样:

upload.onchange= function () {document.getElementById(img.id).src = window.URL.createObjectURL(this.files[0])}

其他方式:

upload.addEventListener('change', function () {document.getElementById(img.id).src =window.URL.createObjectURL(this.files[0])})

The Following code will add File upload and preview field.

<b>This single img works but not in js</b> <br>
<img id="img" alt="your image" width="100" height="100" />
<input type="file" onchange="document.getElementById('img').src = window.URL.createObjectURL(this.files[0])">

<br/>
No of Img <input type="text" id="noi" name="noi" value="" onkeyup="addFields()">
    <br />
<script>
            function addFields(){
            // Number of inputs to create
            var number = document.getElementById("noi").value;
            // Container <div> where dynamic content will be placed
            var container = document.getElementById("container");
            var array = ["CRICTICAL","HIGH","LOW","INFO"];
            // Clear previous contents of the container
            while (container.hasChildNodes()) {
                container.removeChild(container.lastChild);
            }
            for (i=1;i<=number;i++){
                var img = document.createElement("img");
                img.width="100";
                img.height="100";
                img.id="img "+i;

                var upload = document.createElement("input");
                upload.type="file";
//This part is Not Working_______________
                upload.onchange="document.getElementById(img.id).src = window.URL.createObjectURL(this.files[0])";

//________________________________________
                container.appendChild(img);
                container.appendChild(upload);
                container.appendChild(document.createElement("br"));
            }
        }


        </script>
    <div id="container"/>

Problem :

Without the Container appendChild function the code works fine, you can see it in the first three lines of code.

解决方案

You have to run a function inside upload.onchange. Something like this:

upload.onchange= function () {
    document.getElementById(img.id).src = window.URL.createObjectURL(this.files[0])
}

Other way to do:

upload.addEventListener('change', function () {
    document.getElementById(img.id).src = 
    window.URL.createObjectURL(this.files[0])
})

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