根据不同的后缀名，返回相应的后缀类别。

getSuffixIcon.js

var getSuffixIcon = function(type){
    var icon ='unknow';
    var suffix = {
        image:['jpg','png','gif','jpeg'],
        doc:['doc','docx'],
        rar:['rar','zip','tar','gz','7z','tar.gz'],
        xls:['csv','xls']
    }  
    for(var k in suffix){
        if($.inArray(type, suffix[k]) > -1){
            icon = k;
        }    
    }  
    return icon;
}