JS实现图片预览的两种方式

考虑到用户体验，网页的图片上传数据库前，先预览是很有必要的一个步骤，第一可以给用户带来安全感，第二防止图片文件有问题而提交到数据库，占用存储资源。

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那么要实现预览有两种方式：一种是用window.URL.createObjectURl方法对选择的图片数据（可以勉强理解为input的value）生成一个blob对象路径，第二种是用获取 FileReader读取器。

那么无论那种方法，首先都得得到文件数据，获得文件数据是从files集合中获取。

方式一：

代码如下：








	    基本
        文件
        流程
        错误
        SQL
        调试
    

		    
    
	请求信息 : 2026-05-27 05:23:51 HTTP/1.1 GET : /article/gschie.html
运行时间 : 3.1518s ( Load:0.0086s Init:2.5065s Exec:0.6278s Template:0.0089s )
吞吐率 : 0.32req/s
内存开销 : 2,221.19 kb
查询信息 : 12 queries 5 writes 
文件加载 : 36
缓存信息 : 0 gets 0 writes 
配置加载 : 130
会话信息 : SESSION_ID=hh60f2r9rjdc3h61ag9ln31ja1
    
    
        
    
	/www/wwwroot/tsicrk.com/index.php ( 1.09 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/ThinkPHP.php ( 4.61 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Think.class.php ( 12.26 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Storage.class.php ( 1.37 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Storage/Driver/File.class.php ( 3.52 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Mode/common.php ( 2.82 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Common/functions.php ( 53.56 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Hook.class.php ( 4.01 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/App.class.php ( 13.49 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Dispatcher.class.php ( 14.79 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Route.class.php ( 13.36 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Controller.class.php ( 11.23 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/View.class.php ( 7.59 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Behavior/BuildLiteBehavior.class.php ( 3.68 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Behavior/ParseTemplateBehavior.class.php ( 3.88 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Behavior/ContentReplaceBehavior.class.php ( 1.91 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Conf/convention.php ( 11.15 KB )
/www/wwwroot/tsicrk.com/App/Common/Conf/config.php ( 2.14 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Lang/zh-cn.php ( 2.55 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Conf/debug.php ( 1.49 KB )
/www/wwwroot/tsicrk.com/App/Home/Conf/config.php ( 0.31 KB )
/www/wwwroot/tsicrk.com/App/Home/Common/function.php ( 3.33 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Behavior/ReadHtmlCacheBehavior.class.php ( 5.62 KB )
/www/wwwroot/tsicrk.com/App/Home/Controller/ArticleController.class.php ( 6.02 KB )
/www/wwwroot/tsicrk.com/App/Home/Controller/CommController.class.php ( 1.60 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Model.class.php ( 60.11 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Db.class.php ( 32.43 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Db/Driver/Pdo.class.php ( 16.74 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Cache.class.php ( 3.83 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Cache/Driver/File.class.php ( 5.87 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Template.class.php ( 28.16 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Template/TagLib/Cx.class.php ( 22.40 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Template/TagLib.class.php ( 9.16 KB )
/www/wwwroot/tsicrk.com/App/Runtime/Cache/Home/7540f392f42b28b481b30614275e4e55.php ( 17.71 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Behavior/WriteHtmlCacheBehavior.class.php ( 0.97 KB )
/www/wwwroot/tsicrk.com/ThinkPHP/Library/Behavior/ShowPageTraceBehavior.class.php ( 5.24 KB )
    
    
        
    
	[ app_init ] --START--
Run Behavior\BuildLiteBehavior [ RunTime:0.000005s ]
[ app_init ] --END-- [ RunTime:0.000024s ]
[ app_begin ] --START--
Run Behavior\ReadHtmlCacheBehavior [ RunTime:0.000370s ]
[ app_begin ] --END-- [ RunTime:0.000394s ]
[ view_parse ] --START--
[ template_filter ] --START--
Run Behavior\ContentReplaceBehavior [ RunTime:0.000049s ]
[ template_filter ] --END-- [ RunTime:0.000069s ]
Run Behavior\ParseTemplateBehavior [ RunTime:0.006075s ]
[ view_parse ] --END-- [ RunTime:0.006099s ]
[ view_filter ] --START--
Run Behavior\WriteHtmlCacheBehavior [ RunTime:0.000154s ]
[ view_filter ] --END-- [ RunTime:0.000168s ]
[ app_end ] --START--
    
    
        
    
	1064:You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') LIMIT 1' at line 1
 [ SQL语句 ] : SELECT `id`,`pid`,`navname` FROM `cx_nav` WHERE ( id= ) LIMIT 1  
1064:You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') LIMIT 1' at line 1
 [ SQL语句 ] : SELECT `id`,`navname` FROM `cx_nav` WHERE ( id= ) LIMIT 1  
1064:You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 1
 [ SQL语句 ] : SELECT `id`,`navname` FROM `cx_nav` WHERE ( pid= ) 
[8] Undefined index: pid /www/wwwroot/tsicrk.com/App/Home/Controller/ArticleController.class.php 第 47 行.
[8] Undefined index: db_host /www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Db.class.php 第 120 行.
[8] Undefined index: db_port /www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Db.class.php 第 121 行.
[8] Undefined index: db_name /www/wwwroot/tsicrk.com/ThinkPHP/Library/Think/Db.class.php 第 122 行.
    
    
        
    
	    
    
        
    
	    
    
    



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JS实现图片预览的两种方式