In Javascript how do I detect different kinds of elements in an array containing sub arrays and single elements?

I am being given data in an array that contains sub arrays and single elements.
I do not know how many elements in the main array are sub arrays, or how many are single elements, or how many elements will be in a sub array, or where the sub arrays will be in the main array.

Is there a way I can detect the sub arrays or the single elements?

Example:

array[ [1,2,3], 4, 5]

Answer

Loop and check:

[1,2,[4,5],3].forEach((item, i) => {

    if (Array.isArray(item)) {
        console.log(`Item ${i} is an array!`); // Item 2 is an array!
    }
})

Or map to booleans:

[1,2,[4,5],3].map(Array.isArray); // [false, false, true, false]