Array of array subtraction

gistfile1.js

function remove_selected_from_options(arr1, arr2) {
  var filtered_options = [];
	for (var i=0; i < arr1.length; i++) {
		var included = false;
		for (var z=0; z < arr2.length; z++) {
		  if (arr2[z][0] == arr1[i][0]) {
		  	included = true;
		  	break;
		  }
		}
		if (included == false) {
			filtered_options.push(arr1[i]);
		}
	}
	return filtered_options
}

var a = [[1, 'cat'], [2, 'dog'], [3, 'squirrel']];
var b = [[1, 'cat'], [2, 'dog']];
remove_selected_from_options(a, b);

function subAB(a, b) {
  return a.filter(function(itemA, index) {
    return !(b.some(function(itemB) { 
      return itemB[0] === itemA[0];
    }))
  })
}

var a = [[1, 'cat'], [2, 'dog'], [3, 'squirrel']];
var b = [[1, 'cat'], [2, 'dog']];
subAB(a, b)