js中的base64转化

创建一个base64.js文件，将以下代码粘贴进去

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
    }
};