docs: function isPermutation( arr, value ) {
  	var len, N, x, i, j;
  	if ( !isArray( arr ) ) {
  		throw new TypeError( 'isPermutation()::invalid input argument. Second argument must be an array. Value: `' + arr + '`.' );
  	}
  	if ( !isArray( value ) ) {
  		return false;
  	}
  	len = value.length;
  	if ( !len ) {
  		return false;
  	}
  	if ( len !== arr.length ) {
  		return false;
  	}
  	arr = arr.slice();
  	for ( i = 0; i < len; i++ ) {
  		x = value[ i ];
  		N = arr.length;
  
  		// Search for a match. If found, remove it...
  		for ( j = 0; j < N; j++ ) {
  			if ( arr[ j ] === x ) {
  				arr.splice( j, 1 );
  				break;
  			}
  		}
  		// If no match was found, then an element in the `value` array does not exist in the comparison array. Therefore, not a permutation.
  		if ( arr.length === N ) {
  			return false;
  		}
  	}
  	return true;
  }