9/1/2023 0 Comments Js includesIn 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.
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