var a = 1;
var b = a;
b = 2;
console.log(a);  // 1

var obj1 = [];    // 新建一个空数组 obj1
var obj2 = [];    // 新建一个空数组 obj2
console.log(obj1 == obj2);    // false
console.log(obj1 === obj2);   // false

array1.toString() === array2.toString()
// or
JSON.stringify(array1) === JSON.stringify(array2)

// funtion for simple array string[]
isArrayEquals(array1, array2) {
    if(!(array1 || array1)) {
      return false;
    }
    // Compare the length
    if (array1.length != array2.length) {
        return false;
    }
    // 先排序再转化为string比较
    if (array1.sort().toString() === array2.sort().toString()) {
    // if (JSON.stringify(array1.sort()) === JSON.stringify(array2.sort()) ) {
        return true;
    }
    return false;
}

// prototype 方法
// Warn if overriding existing method
if (Array.prototype.equals) {
    console.warn("Overriding existing Array.prototype.equals. Possible causes: New API defines the method, there's a framework conflict or you've got double inclusions in your code.");
}

Array.prototype.equals = function(array) {
  if (!array) {
    return false;
  }
  if (this.length !== array.length) {
    return false;
  }
  for (var i = 0; i < this.length; i++) {
    if (this[i] instanceof Array && array[i] instanceof Array) {
      if (!this[i].equals(array[i])) {
        return false;
      }
    }
    else if (this[i] !== array[i]) {
      return false;
    }
  }
  return true;
}

// funtion for all kinds of array
isArrayEquals(array1, array2) {
    if(!(array1 || array1)) {
      return false;
    }
    // Compare the length
    if (array1.length != array2.length) {
        return false;
    }

    for (var i = 0; i < array1.length; i++) {
        // check wheather it's nested arrays
        if (array1[i] instanceof Array && array2[i] instanceof Array) {
            // Recursion
            if (!isArrayEquals(array1[i],array2[i]))
                return false;       
        } else if (this[i] != array[i]) {
            return false;   
        }           
    }       
    return true;
}

Object.prototype.equals = function(object2) {
    //For the first loop, we only check for types
    for (propName in this) {
        //Check for inherited methods and properties - like .equals itself
        //https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty
        //Return false if the return value is different
        if (this.hasOwnProperty(propName) != object2.hasOwnProperty(propName)) {
            return false;
        }
        //Check instance type
        else if (typeof this[propName] != typeof object2[propName]) {
            //Different types => not equal
            return false;
        }
    }
    //Now a deeper check using other objects property names
    for (propName in object2) {
        //We must check instances anyway, there may be a property that only exists in object2
            //I wonder, if remembering the checked values from the first loop would be faster or not 
        if (this.hasOwnProperty(propName) != object2.hasOwnProperty(propName)) {
            return false;
        }
        else if (typeof this[propName] != typeof object2[propName]) {
            return false;
        }
        //If the property is inherited, do not check any more (it must be equa if both objects inherit it)
        if(!this.hasOwnProperty(propName))
          continue;

        //Now the detail check and recursion

        //This returns the script back to the array comparing
        /**REQUIRES Array.equals**/
        if (this[propName] instanceof Array && object2[propName] instanceof Array) {
                   // recurse into the nested arrays
           if (!this[propName].equals(object2[propName]))
                        return false;
        }
        else if (this[propName] instanceof Object && object2[propName] instanceof Object) {
                   // recurse into another objects
                   //console.log("Recursing to compare ", this[propName],"with",object2[propName], " both named ""+propName+""");
           if (!this[propName].equals(object2[propName]))
                        return false;
        }
        //Normal value comparison for strings and numbers
        else if(this[propName] != object2[propName]) {
           return false;
        }
    }
    //If everything passed, let's say YES
    return true;
}