Home > Developer > Web Develop

Front End Implementation input[type= ' file ' upload picture preview effect

Source: Internet
Author: User
Tags base64
Developer on Alibaba Coud: Build your first app with APIs, SDKs, and tutorials on the Alibaba Cloud. Read more ＞

JavaScript is known to be in the design of security considerations, is not allowed to read and write local files (reason please Baidu);

But in the actual project application, often uses to upload the picture, and lets the user preview the picture directly. For this approach there are two ways to achieve: first, the front and back of the interaction, the background image address back to the front;

Second, what I wrote today, using the filereader Object--Allows the Web application to asynchronously read the contents of a file (or raw data buffer) stored on the user's computer, which optimizes the image loading speed and reduces the bandwidth-consuming problem of the method;

However, there is a problem with this method compatibility, mainly IE browser (ie10 above no problem), this article does not discuss compatibility issues, the code is as follows:

<!DOCTYPE HTML><HTML>    <Head>        <MetaCharSet= "UTF-8">        <title></title>        <Metaname= "Viewport"content= "Width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no" />        <styletype= "Text/css">#preview{Display:Inline-block;width:2.56rem;Height:2.56rem;position:relative;Background-image:URL (img/iconfont-tianjia.png);background-repeat:no-repeat;background-size:cover;            }#file{width:100%;Height:100%;Opacity:0;position:Absolute; Left:0;Top:0;cursor:Pointer;Z-index:5;            }        </style>    </Head>    <Body>        <DivID= "Preview">            <inputtype= "File"Accept= "image/*"ID= "File"value="" />        </Div>        <Scripttype= "Text/javascript">            varPreview=Document.queryselector ('#preview'); varElefile=Document.queryselector ('#file'); Elefile.addeventlistener (' Change', function() {                varfile=  This. files[0]; //confirm that the selected file is a picture                if(File.type.indexOf ("Image") == 0) {                    varReader= NewFileReader ();                                        Reader.readasdataurl (file); Reader.onload= function(e) {//Picture Base64                        varNewurl=  This. Result; Preview.style.backgroundImage= 'URL (' +Newurl+ ')';                };        }            }); </Script>    </Body></HTML>

For direct multiplexing, thefilereader object is then displayed by converting the image URL into the base64 format.

Front End Implementation input[type= ' file ' upload picture preview effect

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

Related Keywords:
input type file upload image html input type file upload input type file image upload php multiple file upload with preview input type picture python front end framework front end load balancer

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

What's Trending
Top 10 Tags
datastax versions naming convention zookeeper client class definition md5 microsoft sql server 2005 data structures exception handling error handling
Top 10 Keywords
microsoft download center down wordpress address url site address url wordpress address url windows installer 4 0 download 302 not found web address url definition site address url wordpress db2 integer mac os installation step by step pdf abbreviation for return

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

Get Started for Free

  • Sales Support

    1 on 1 presale consultation

    Chat Contact Sales

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

    Open a Ticket

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.

    Learn More