HTML5原生支持Base64编码解码

该方法仅支持IE10+、chrome、等现代浏览器。

适合用于原生支持的

(function(){
    var Base64 = {
        encode : function(str){
            return window.btoa(unescape(encodeURIComponent(str)));
        },
        decode : function(str){
            return decodeURIComponent(escape(window.atob(str)));
        }
    };
    window.BASE64 = Base64;
})();

旧版本兼容

(function() {
    if (!window.btoa) {
        var a = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
        window.btoa = function(c) {
            var d = "";
            var m, k, h = "";
            var l, j, g, f = "";
            var e = 0;
            do {
                m = c.charCodeAt(e++);
                k = c.charCodeAt(e++);
                h = c.charCodeAt(e++);
                l = m >> 2;
                j = ((m & 3) > 4);
                g = ((k & 15) > 6);
                f = h & 63;
                if (isNaN(k)) {
                    g = f = 64
                } else {
                    if (isNaN(h)) {
                        f = 64
                    }
                }
                d = d + a.charAt(l) + a.charAt(j) + a.charAt(g) + a.charAt(f);
                m = k = h = "";
                l = j = g = f = ""
            } while (e > 4);
                k = ((j & 15) > 2);
                h = ((g & 3)