javascript input image upload and preview, FileReader preview image

FileReader is an important API for front-end file processing, especially for image processing. If you want to know the principle of image processing, you will never be able to bypass it.

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
		.file-ipt{position: absolute;left:0;top: 0;opacity: 0;width: 50px;height: 25px;} //The input box is made transparent here, and then absolutely positioned on the button .btn{width: 50px;height: 25px; background-color: skyblue;color: white;margin-right: 80px;border: none;border-radius: 10px;font-size: 8px;}
		</style>
	</head>
	<body>
		<button class="btn">Picture</button>
		<input type="file" id="file" accept="image/jpg,imgae/jpeg,image/png" class="file-ipt" onchange="insertimg(this);"><br>
		<img src="" id="img1" alt="">
		<script language="javascript">
			function insertimg(img){
				var rd=new FileReader();
				files=img.files[0];
				var filetype = files.type.slice(6,10);
				if(filetype!='jpg'&&filetype!='jpeg'&&filetype!='png'){
					alert('Only png, jpeg, jpg image formats are supported');
					return;
				}else{
					rd.readAsDataURL(files);
					rd.onloadend=function(e){
						document.getElementById('img1').src=e.target.result;
						document.getElementById('img1').style.width="300px";
						document.getElementById('img1').style.height="auto";
					};
				}
			}
		</script>
	</body>
</html>

Knowledge point supplement: JS input file picture upload preview effect

First, you can learn about the file and FileReader APIs. After selecting one or more files, you can access one or more File objects representing the selected files. These objects are contained in a FileList object. All <input> elements with a type attribute of file have a files attribute to store the files selected by the user. Files has a length property and an item method. We can get the file object of our choice through files[index] or files.item(index). You can use the change event to listen for the input file input completion event.

HTML code:

 <ul class="crgoods_uploadUl clearfix">
     <li><img src="img/product1.jpg"></li>
     <li><img src="img/product1.jpg"></li>
     <li class="add"><i>+</i>Up to 20 pictures<input type="file" class="liAdd_flie" onchange="liUploadImg(this)"></li>
</ul>

js code:

//Product album picture upload preview function liUploadImg(file){     
        if (file.files && file.files[0]){
            var reader = new FileReader();
            reader.onload = function(evt){ 
                // imgUpload.src = evt.target.result;
                $('.crgoods_uploadUl li.add').before('<li><img src="'+evt.target.result+'"></li>');   
            }
            reader.readAsDataURL(file.files[0]);
        }else{ 
            var sFilter = 'filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale,src="';
            file.select();
            var src = document.selection.createRange().text;
            imgUpload.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src = src;
        }
    }

In addition, the detailed API can refer to https://segmentfault.com/a/1190000006600936

Here is an example:

This is the end of this article about javascript input image upload and preview, FileReader preview image. For more related javascript file upload and preview content, please search 123WORDPRESS.COM's previous articles or continue to browse the following related articles. I hope everyone will support 123WORDPRESS.COM in the future!

You may also be interested in:

js to realize image upload and preview function
js to upload pictures and display them normally
js method to realize the preview of uploaded pictures
js to achieve instant display effect of picture upload

<<: How to reasonably use the redundant fields of the database

>>: Tutorial on how to modify the IP address of a Linux virtual machine, check the gateway, and configure the network environment

onfocus="this.blur()" is hated by blind webmasters

javascript input image upload and preview, FileReader preview image

onfocus="this.blur()" is hated by blind webmasters

Three methods of inheritance in JavaScript

A brief discussion on whether too many MySQL data queries will cause OOM

Nginx rush purchase current limiting configuration implementation analysis

Use jQuery to fix the invalid page anchor point problem under iframe

css input[type=file] style beautification (input upload file style)

Description of the hr tag in various browsers

Detailed graphic explanation of installing MySQL database and configuring Java project on Linux

Learn MySQL index pushdown in five minutes

MySQL full-text search Chinese solution and example code

Recommend

Split and merge tables in HTML (colspan, rowspan)

How to upload projects to Code Cloud in Linux system

Native js implements custom scroll bar component

Solution to CSS anchor positioning being blocked by the top fixed navigation bar

Vue+elementUI component recursively implements foldable dynamic rendering multi-level sidebar navigation

What does it mean to add a question mark (?) after the CSS link address?

Example of how to identify the user using a linux Bash script

MySQL database master-slave configuration tutorial under Windows

Three ways to implement animation in CSS3

Detailed explanation of mysql backup and recovery

The latest popular script Autojs source code sharing

Detailed explanation of generic cases in TypeScript

Detailed explanation of the difference between MySQL normal index and unique index

Better looking CSS custom styles (title h1 h2 h3)

How to view available network interfaces in Linux