If an existing, unvisited element of the array is changed by callback, its value passed to the callback will be the value at the time findIndex() visits the element's index.Įlements that are deleted are still visited. callback will not process the elements appended to the array after the call to findIndex() begins. The range of elements processed by findIndex() is set before the first invocation of callback. If it is not provided, then undefined is used. If a thisArg parameter is passed to findIndex(), it will be used as the this inside each invocation of the callback. If callback never returns a truthy value (or the array's length is 0), findIndex() returns -1.Įdge case alert: Unlike other array methods such as Array.some(), callback is run even for indexes with unassigned values.Ĭallback is invoked with three arguments: If such an element is found, findIndex() immediately returns the element's index. The findIndex() method executes the callback function once for every index in the array until it finds the one where callback returns a truthy value. The index of the first element in the array that passes the test. thisArg Optional Optional object to use as this when executing callback.

array Optional The array findIndex() was called upon. index Optional The index of the current element being processed in the array. It takes three arguments: element The current element being processed in the array.

Syntax arr.findIndex( callback( element] ))Ī function to execute on each value in the array until the function returns true, indicating that the satisfying element was found. See also the find() method, which returns the value of an array element, instead of its index. If you'd like to contribute to the interactive examples project, please clone and send us a pull request. The source for this interactive example is stored in a GitHub repository.

Javascript array findindex