JavaScript

以下代码摘自：http://cryptojs.altervista.org/encoding/Base64.html

function base64_encode(str) {
    if (window.btoa) // Internet Explorer 10 and above
    return window.btoa(unescape(encodeURIComponent(str)));
    else {
        // Cross-Browser Method (compressed)
        // Create Base64 Object
        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(/
/g, "
");
                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
            }
        }
        // Encode the String
        return Base64.encode(unescape(encodeURIComponent(str)));
    }
}

function base64_decode(str) {
    if (window.atob) // Internet Explorer 10 and above
    return decodeURIComponent(escape(window.atob(str)));
    else {
        // Cross-Browser Method (compressed)
        // Create Base64 Object
        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(/
/g, "
");
                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
            }
        }
        // Encode the String
        return decodeURIComponent(escape(Base64.decode(str)));
    }
}

普通压缩：

function base64_encode(str){if(window.btoa)return window.btoa(unescape(encodeURIComponent(str)));else{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(/
/g,"
");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}}return Base64.encode(unescape(encodeURIComponent(str)))}}function base64_decode(str){if(window.atob)return decodeURIComponent(escape(window.atob(str)));else{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(/
/g,"
");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}}return decodeURIComponent(escape(Base64.decode(str)))}}