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Use () method to check whether all elements in an array pass the test implemented by the provided function.To check if every element of the first array exists in the second array, you can do the following: In JavaScript, you can check if every element of the first array exists in the second array, in the following ways: log ( "Visited index", index, "with value", value ) } ) // Visited index 0 with value 0 // Visited index 1 with value 1 // Visited index 2 with value undefined // Visited index 3 with value undefined // Visited index 4 with value undefined // Visited index 5 with value 5 // Visited index 6 with value 6 // Shows all indexes, including deletedĪrray. Declare array with no elements at indexes 2, 3, and 4 const array = // Shows all indexes, not just those with assigned valuesĬonsole. Deleted elements are visited as if they were undefined. If an existing, yet-unvisited element of the array is changed by callbackFn, its value passed to the callbackFn will be the value at the time that element gets visited.Changes to already-visited indexes do not cause callbackFn to be invoked on them again.callbackFn will not visit any elements added beyond the array's initial length when the call to find() began.Note, however, that the length of the array is saved before the first invocation of callbackFn. Empty slots in sparse arrays behave the same as undefined.įind() does not mutate the array on which it is called, but the function provided as callbackFn can.

If callbackFn never returns a truthy value, find() returns undefined.ĬallbackFn is invoked for every index of the array, not just those with assigned values.

find() then returns that element and stops iterating through the array. It calls a provided callbackFn function once for each element in an array in ascending-index order, until callbackFn returns a truthy value. The find() method is an iterative method.