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alert([]==[]);  // false

alert([]===[]);  // false

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JSON.stringify(a1) == JSON.stringify(a2)

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a1.toString() == a2.toString()

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// 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."

// attach the .equals method to Array's prototype to call it on any array

Array.prototype.equals = function (array) {

  // if the other array is a falsy value, return

  if (!array)

    return false;

  // compare lengths - can save a lot of time

  if (this.length != array.length)

    return false;

  for (var i = 0, l = this.length; i < l; i++) {

    // Check if we have nested arrays

    if (this[i] instanceof Array && array[i] instanceof Array) {

      // recurse into the nested arrays

      if (!this[i].equals(array[i]))

        return false;   

    }     

    else if (this[i] != array[i]) {

      // Warning - two different object instances will never be equal: {x:20} != {x:20}

      return false; 

    }     

  }   

  return true;

}

// Hide method from for-in loops

Object.defineProperty(Array.prototype, "equals", {enumerable: false});

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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;

}