JSON.stringify([1,2,3].sort()) === JSON.stringify([3,2,1].sort()); //true

[1,2,3].sort().toString() === [3,2,1].sort().toString(); //true

let cmp = ( x, y ) => {
// If both x and y are null or undefined and exactly the same
    if ( x === y ) {
      return true;
    }
// If they are not strictly equal, they both need to be Objects
    if ( ! ( x instanceof Object ) || ! ( y instanceof Object ) ) {
      return false;
    }
//They must have the exact same prototype chain,the closest we can do is
//test the constructor.
    if ( x.constructor !== y.constructor ) {
      return false;
    }
    for ( var p in x ) {
      //Inherited properties were tested using x.constructor === y.constructor
      if ( x.hasOwnProperty( p ) ) {
        // Allows comparing x[ p ] and y[ p ] when set to undefined
        if ( ! y.hasOwnProperty( p ) ) {
          return false;
        }
        // If they have the same strict value or identity then they are equal
        if ( x[ p ] === y[ p ] ) {
          continue;
        }
        // Numbers, Strings, Functions, Booleans must be strictly equal
        if ( typeof( x[ p ] ) !== "object" ) {
          return false;
        }
        // Objects and Arrays must be tested recursively
        if ( ! Object.equals( x[ p ], y[ p ] ) ) {
          return false;
        }
      }
    }
    for ( p in y ) {
      // allows x[ p ] to be set to undefined
      if ( y.hasOwnProperty( p ) && ! x.hasOwnProperty( p ) ) {
        return false;
      }
    }
    return true;
};