Checking if an array has an item with the vanilla JS Array.protype.includes() method
In yesterday’s article, I mentioned the
Array.prototype.includes() method. Today, I wanted to look at how it works.
Array.prototype.includes() method accepts the value to search for in an array as an argument, and returns a boolean,
true if it’s in the array, and
false if it’s not.
let wizards = ['Merlin', 'Ursula', 'Gandalf', 'Radagast']; // returns true let hasUrsula = wizards.includes('Ursula'); // returns false let hasMorgana = wizards.includes('Morgana');
If you want to start searching at a specific index, you can pass that in as an optional second argument.
// check if 'Radagast' is in the array anywhere from index 2 on wizards.includes('Radagast', 2);
Array.prototype.includes() method can only be used with shallow arrays containing primitive values. Arrays with nested arrays or objects won’t work, because they fail the internal equality that the method runs.