The findIndex() method of TypedArray instances returns the index of the first element in a typed array that satisfies the provided testing function. If no elements satisfy the testing function, -1 is returned. This method has the same algorithm as Array.prototype.findIndex.
Syntax
findIndex(callbackFn)
findIndex(callbackFn, thisArg)
Parameters
callbackFn- : A function to execute for each element in the typed array. It should return a truthy value to indicate a matching element has been found, and a falsy value otherwise. The function is called with the following arguments:
element- : The current element being processed in the typed array.
index- : The index of the current element being processed in the typed array.
array- : The typed array
findIndex()was called upon.
- : The typed array
- : A function to execute for each element in the typed array. It should return a truthy value to indicate a matching element has been found, and a falsy value otherwise. The function is called with the following arguments:
thisArg- : A value to use as
thiswhen executingcallbackFn. See iterative methods.
- : A value to use as
Return value
The index of the first element in the typed array that passes the test. Otherwise, -1.
Description
See Array.prototype.findIndex for more details. This method is not generic and can only be called on typed array instances.
Examples
Find the index of a prime number in a typed array
The following example finds the index of an element in the typed array that is a prime
number (or returns -1 if there is no prime number).
function isPrime(element, index, array) {
let start = 2;
while (start <= Math.sqrt(element)) {
if (element % start++ < 1) {
return false;
}
}
return element > 1;
}
const uint8 = new Uint8Array([4, 6, 8, 12]);
const uint16 = new Uint16Array([4, 6, 7, 12]);
console.log(uint8.findIndex(isPrime)); // -1, not found
console.log(uint16.findIndex(isPrime)); // 2