The arrow function will be holding the filter criteria. The Array.filter() function accepts an inline function or arrow function as a parameter. If you use Array#includes(), make sure you add a polyfill for older browsers.find((keyword) => ) But since Array#includes() was introduced in ES2016, it is not supported in any version of Internet Explorer or Node.js versions before 6.0.0. Array contains 1 element, 'NaN' const arr = Īrray#includes() is generally the better choice, because you don't need to type out != -1 and because it has slightly better equality semantics. In other words, Array#indexOf() cannot find

Unlike Array#includes(), Array#indexOf() uses the same semantics as the = However, using bitwise NOT is generally bad practice because it sacrifices This is a handy trick to avoid having to write out != -1. Given an integer v, ~v = -(v + 1), so ~v = 0 only if v = -1. Some codebases, you may see ~arr.indexOf(v) instead, where ~ is the To check whether arr contains v, you would use arr.indexOf(v) != -1.

const arr = Īrr.indexOf( 'D') // -1 // To check whether an array contains a given value, you should use the // below check. The indexOf() function returns the first index in the array at which it found valueToFind, or -1 otherwise. The Array#indexOf() function is a common alternative to includes(). `Array#includes()` // smooths out those rough edges.Īrr = Number.NaN // false indexOf() Array contains 1 element, 'NaN' const arr = Īrr.includes( Number.NaN) // true // The `=` operator has some quirks with NaN. The technical term for this equality check is sameValueZero. The Array#includes() function will find NaN in an array. Semantics as the = operator (no type coercion), with the exception The Array#includes() function checks for equality using the same It takes a parameter valueToFind, and returns true if some element in the array is equal to valueToFind. The Array#includes() function was introduced in ECMAScript 2016. To determine whether arr contains the string 'B', you can use Array#includes() or Array#indexOf(). Suppose you have a simple array with 3 elements: const arr = Given a JavaScript array, there are two built-in array methods you can use to determine whether the array contains a given element.

Javascript array includes