前端：

//加密、解密算法封装：
function Base64() {
    // private property
    let _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
    // public method for encoding
    this.encode = function(input) {
        var output = "";
        var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
        var i = 0;
        input = _checkChar(input)
        input = _utf8_encode(input);
        // console.log(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 +
                _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +
                _keyStr.charAt(enc3) + _keyStr.charAt(enc4);
        };
        output = output.replace('+','-').replace('/','_');// 这个后台识别不了+，所以替换了一下，这个也可以不用替换，视实际情况定
        return output;
    };
 
    // public method for decoding
    this.decode = function(input) {
        var output = "";
        var chr1, chr2, chr3;
        var enc1, enc2, enc3, enc4;
        var i = 0;
        if (typeof(input) == String) {
            input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
        }else{
            return input
        }
        while (i < input.length) {
            enc1 = _keyStr.indexOf(input.charAt(i++));
            enc2 = _keyStr.indexOf(input.charAt(i++));
            enc3 = _keyStr.indexOf(input.charAt(i++));
            enc4 = _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 = _utf8_decode(output);
        output = _returnJson(output);
        return output;
    }
 
    // private method for UTF-8 encoding
    let _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);
            }
 
        }
        // console.log(utftext);
        return utftext;
    }
 
    // private method for UTF-8 decoding
    let _utf8_decode = function(utftext) {
        var string = "";
        var i = 0;
        var c1, c2, c3;
        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;
    }
    let _checkChar = function(textJson) {
        var pattern = new RegExp("[\u4E00-\u9FA5]+");
        for (let item in textJson) {
            if (pattern.test(textJson[item])) {
                textJson[item] = encodeURIComponent(textJson[item]);
            }
        }
        return JSON.stringify(textJson);
    }
    let _returnJson = function(textString) {
        let res = JSON.parse(textString);
        for (let item in res) {
            res[item] = decodeURIComponent(res[item]);
        }
        return res;
    }
}
 
export {
    Base64,
}

后端：

if (!function_exists('base64_urlSafeEncode')) {
    /**
     * 对提供的数据进行urlsafe的base64编码。
     *
     * @param string $data 待编码的数据，一般为字符串
     *
     * @return string 编码后的字符串
     * @link http://developer.qiniu.com/docs/v6/api/overview/appendix.html#urlsafe-base64
     */
    function base64_urlSafeEncode($data)
    {
        $find = array('+', '/');
        $replace = array('-', '_');
        return str_replace($find, $replace, base64_encode($data));
    }
}
if (!function_exists('base64_urlSafeDecode')) {
    /**
     * 对提供的urlsafe的base64编码的数据进行解码
     *
     * @param string $str 待解码的数据，一般为字符串
     *
     * @return string 解码后的字符串
     */
    function base64_urlSafeDecode($str)
    {
        $find = array('-', '_');
        $replace = array('+', '/');
        return base64_decode(str_replace($find, $replace, $str));
    }
}