function equal(a, b) {
  const typeA = Object.prototype.toString.call(a);
  const typeB = Object.prototype.toString.call(b);
  if (typeA === typeB) {
    if (typeA === '[object Object]') {
      // Object
      let resultNum = 0;
      let keyA = Object.keys(a);
      let keyB = Object.keys(b);
      if (keyA.length !== keyB.length) return false;
      for (let i = 0;i < keyA.length;i++) {
        let targetKey = keyA[i];
        if (equal(b[targetKey], a[targetKey])) {
          resultNum++;
        } else {
          return false;
        }
      }
      return resultNum === keyA.length;
    } else if (typeA === '[object Array]') {
      // Array
      if (a.length !== b.length) return false;
      for (let i = -1, item = a[i];item=a[++i];){
        if (!equal(item, b[i])) {
          return false;
        }
      }
      return true;
    } else {
      // Not Support
      return a === b;
    }
  } else {
    return false;
  }
}

let obj1 = { a: [1, '2'], b: 2};
let obj2 = { b: 2, a: [1, '2']};
let arr1 = [1, 2, { a: 1, b: 2 }, 9];
let arr2 = [1, 2, { b: 2, a: 1 }, 9];

console.log("equal(obj1, obj2)", equal(obj1, obj2));
console.log("equal(arr1, arr2)", equal(arr1, arr2));
console.log("equal(obj1, arr1)", equal(obj1, arr1));