base64转码js文件备份

base64对外提供两种方法，一个加密Base64.encode(str),一个解密Base64.decode(str)

var Base64=
    {
        _keyStr:"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
        encode:function(e){
            var t="";
            var n,r,i,s,o,u,a;
            var f=0;
            e=Base64._utf8_encode(e);
            while(f<e.length){
                n=e.charCodeAt(f++);
                r=e.charCodeAt(f++);
                i=e.charCodeAt(f++);
                s=n>>2;
                o=(n&3)<<4|r>>4;
                u=(r&15)<<2|i>>6;
                a=i&63;
                if(isNaN(r)){
                    u=a=64
                }else if(isNaN(i)){
                    a=64
                }
                t=t+this._keyStr.charAt(s)+this._keyStr.charAt(o)+this._keyStr.charAt(u)+this._keyStr.charAt(a)
            }
            return t
        },
        decode:function(e){
            var t="";
            var n,r,i;
            var s,o,u,a;
            var f=0;
            e=e.replace(/[^A-Za-z0-9+/=]/g,"");
            while(f<e.length){
                s=this._keyStr.indexOf(e.charAt(f++));
                o=this._keyStr.indexOf(e.charAt(f++));
                u=this._keyStr.indexOf(e.charAt(f++));
                a=this._keyStr.indexOf(e.charAt(f++));
                n=s<<2|o>>4;
                r=(o&15)<<4|u>>2;
                i=(u&3)<<6|a;
                t=t+String.fromCharCode(n);
                if(u!=64){
                    t=t+String.fromCharCode(r)
                }
                if(a!=64){
                    t=t+String.fromCharCode(i)
                }
            }
            t=Base64._utf8_decode(t);
            return t
        },
        _utf8_encode:function(e){
            e=e.replace(/rn/g,"n");
            var t="";
            for(var n=0;n<e.length;n++){
                var r=e.charCodeAt(n);
                if(r<128){
                    t+=String.fromCharCode(r)
                }else if(r>127&&r<2048){
                    t+=String.fromCharCode(r>>6|192);
                    t+=String.fromCharCode(r&63|128)
                }else{
                    t+=String.fromCharCode(r>>12|224);
                    t+=String.fromCharCode(r>>6&63|128);
                    t+=String.fromCharCode(r&63|128)
                }
            }
            return t
        },
        _utf8_decode:function(e){
            var t="";
            var n=0;
            var r=c1=c2=0;
            while(n<e.length){
                r=e.charCodeAt(n);
                if(r<128){
                    t+=String.fromCharCode(r);
                    n++
                }else if(r>191&&r<224){
                    c2=e.charCodeAt(n+1);
                    t+=String.fromCharCode((r&31)<<6|c2&63);
                    n+=2
                }else{
                    c2=e.charCodeAt(n+1);
                    c3=e.charCodeAt(n+2);
                    t+=String.fromCharCode((r&15)<<12|(c2&63)<<6|c3&63);
                    n+=3
                }
            }
            return t
        }
    };