Object() without the new keyword or .create method

Question

I was looking on MDN for a polyfill for Array.prototype.includes() and I came across the Object() syntax below:

if (!Array.prototype.includes) {
   Array.prototype.includes = function(searchElement /*, fromIndex*/) {
'use strict';
if (this == null) {
  throw new TypeError('Array.prototype.includes called on null or undefined');
}
//This is the line in question
var O = Object(this);
var len = parseInt(O.length, 10) || 0;
if (len === 0) {
  return false;
}
var n = parseInt(arguments[1], 10) || 0;
var k;
if (n >= 0) {
  k = n;
} else {
  k = len + n;
  if (k < 0) {k = 0;}
}
var currentElement;
while (k < len) {
  currentElement = O[k];
  if (searchElement === currentElement ||
     (searchElement !== searchElement && currentElement !== currentElement)) { // NaN !== NaN
    return true;
  }
  k++;
}
  return false;
  };
}

What is Object(this) doing and what is the purpose of this in this case?

Answer 1

Object(...) converts the passed value to an object. It simply returns the value itself if it is already an object, otherwise wit will create a new object and return that.

From the spec :

When Object is called as a function rather than as a constructor, it performs a type conversion.

Example:

var obj = Object("foo");
// same as 
// var obj = new String("foo");

what is the purpose of this in this case?

It ensures that the value is an object, not a primitive. The implementation just follows the spec :

1. Let O be ? ToObject(this value).