关于微信小程序端base64解码问题

由于atob是浏览器端的，对于微信小程序不支持，导致模拟器【开发工具】显示正常，但真机异常解析失败问题，微信小程序原有的api，官方文档中也废弃了

解决方案：

调用：

const decodedString = base64_url_decode(res.data);
const jsonData = JSON.parse(decodedString);

weAtob  解密处理文件包 ：

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
var b64re = /^(?:[A-Za-z\d+\/]{4})*?(?:[A-Za-z\d+\/]{2}(?:==)?|[A-Za-z\d+\/]{3}=?)?$/;
exports.weBtoa = function (string) {
  string = String(string);
  var bitmap, a, b, c, result = "", i = 0, rest = string.length % 3;
  for (; i < string.length;) {
    if ((a = string.charCodeAt(i++)) > 255 ||
      (b = string.charCodeAt(i++)) > 255 ||
      (c = string.charCodeAt(i++)) > 255)
      throw new TypeError("Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.");
    bitmap = (a << 16) | (b << 8) | c;
    result += b64.charAt(bitmap >> 18 & 63) + b64.charAt(bitmap >> 12 & 63) +
      b64.charAt(bitmap >> 6 & 63) + b64.charAt(bitmap & 63);
  }
  return rest ? result.slice(0, rest - 3) + "===".substring(rest) : result;
};
exports.weAtob = function (string) {
  string = String(string).replace(/[\t\n\f\r ]+/g, "");
  if (!b64re.test(string))
    throw new TypeError("Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.");
  string += "==".slice(2 - (string.length & 3));
  var bitmap, result = "", r1, r2, i = 0;
  for (; i < string.length;) {
    bitmap = b64.indexOf(string.charAt(i++)) << 18 | b64.indexOf(string.charAt(i++)) << 12 |
      (r1 = b64.indexOf(string.charAt(i++))) << 6 | (r2 = b64.indexOf(string.charAt(i++)));
    result += r1 === 64 ? String.fromCharCode(bitmap >> 16 & 255) :
      r2 === 64 ? String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255) :
        String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255, bitmap & 255);
  }
  return result;
};
function b64DecodeUnicode(str) {
  return decodeURIComponent(exports.weAtob(str).replace(/(.)/g, function (p) {
    var code = p.charCodeAt(0).toString(16).toUpperCase();
    if (code.length < 2) {
      code = "0" + code;
    }
    return "%" + code;
  }));
}
exports.base64_url_decode = function (str) {
  var output = str.replace(/-/g, "+").replace(/_/g, "/");
  switch (output.length % 4) {
    case 0:
      break;
    case 2:
      output += "==";
      break;
    case 3:
      output += "=";
      break;
    default:
      throw "Illegal base64url string!";
  }
  try {
    return b64DecodeUnicode(output);
  }
  catch (err) {
    return exports.weAtob(output);
  }
}
function weappJwtDecode(token, options) {
  if (typeof token !== "string") {
    throw ("Invalid token specified");
  }
  options = options || {};
  var pos = options.header === true ? 0 : 1;
  try {
    return JSON.parse(base64_url_decode(token.split(".")[pos]));
  }
  catch (e) {
    throw ("Invalid token specified: " + e.message);
  }
}
exports.default = weappJwtDecode;