在window对象下有两个api,可以对ASCII编码进行编译,得到base64位的字符串

1. btoa:编码为base64
2. atob:解码为ASCII码

此种方法不能对中文进行操作,因为ASCII码中没有中文,如果编码会得到乱码

要编码中文可以先用encodeURIComponent() 对字符串进行转义,转义后再btoa()成base64就可以,

兼容性:不兼容ie9及以下老版本

兼容ie9以下需要自己封装:

var Base64 = {// private property_keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",// public method for encodingencode : function (input) {    var output = "";    var chr1, chr2, chr3, enc1, enc2, enc3, enc4;    var i = 0;    input = Base64._utf8_encode(input);    while (i < input.length) {        chr1 = input.charCodeAt(i++);        chr2 = input.charCodeAt(i++);        chr3 = input.charCodeAt(i++);        enc1 = chr1 >> 2;        enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);        enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);        enc4 = chr3 & 63;        if (isNaN(chr2)) {            enc3 = enc4 = 64;        } else if (isNaN(chr3)) {            enc4 = 64;        }        output = output +        this._keyStr.charAt(enc1) + this._keyStr.charAt(enc2) +        this._keyStr.charAt(enc3) + this._keyStr.charAt(enc4);    }    return output;},// public method for decodingdecode : function (input) {    var output = "";    var chr1, chr2, chr3;    var enc1, enc2, enc3, enc4;    var i = 0;    input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");    while (i < input.length) {        enc1 = this._keyStr.indexOf(input.charAt(i++));        enc2 = this._keyStr.indexOf(input.charAt(i++));        enc3 = this._keyStr.indexOf(input.charAt(i++));        enc4 = this._keyStr.indexOf(input.charAt(i++));        chr1 = (enc1 << 2) | (enc2 >> 4);        chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);        chr3 = ((enc3 & 3) << 6) | enc4;        output = output + String.fromCharCode(chr1);        if (enc3 != 64) {            output = output + String.fromCharCode(chr2);        }        if (enc4 != 64) {            output = output + String.fromCharCode(chr3);        }    }    output = Base64._utf8_decode(output);    return output;},// private method for UTF-8 encoding_utf8_encode : function (string) {    string = string.replace(/\r\n/g,"\n");    var utftext = "";    for (var n = 0; n < string.length; n++) {        var c = string.charCodeAt(n);        if (c < 128) {            utftext += String.fromCharCode(c);        }        else if((c > 127) && (c < 2048)) {            utftext += String.fromCharCode((c >> 6) | 192);            utftext += String.fromCharCode((c & 63) | 128);        }        else {            utftext += String.fromCharCode((c >> 12) | 224);            utftext += String.fromCharCode(((c >> 6) & 63) | 128);            utftext += String.fromCharCode((c & 63) | 128);        }    }    return utftext;},// private method for UTF-8 decoding_utf8_decode : function (utftext) {    var string = "";    var i = 0;    var c = c1 = c2 = 0;    while ( i < utftext.length ) {        c = utftext.charCodeAt(i);        if (c < 128) {            string += String.fromCharCode(c);            i++;        }        else if((c > 191) && (c < 224)) {            c2 = utftext.charCodeAt(i+1);            string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));            i += 2;        }        else {            c2 = utftext.charCodeAt(i+1);            c3 = utftext.charCodeAt(i+2);            string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));            i += 3;        }    }    return string;}}

完