直接上代碼，摘自https://blog.csdn.net/qq_34627459/article/details/79569313，好人一生平安

function getObjectURL(file) {  
     var url = null;  
     if (window.createObjcectURL != undefined) {  
         url = window.createOjcectURL(file);  
     } else if (window.URL != undefined) {  
         url = window.URL.createObjectURL(file);  
     } else if (window.webkitURL != undefined) {  
         url = window.webkitURL.createObjectURL(file);  
     }  
     return url;  
 }
 //使用方法
 $("#file").change(function(){
     var file = this.files[0];
     var url = getObjectURL(file);//blob:http://doamin.com/5376c16a-02f9-489f-b30c-97a1808d5724
 });