const arraySparse = [1,3,,7]
let numCallbackRuns = 0
arraySparse.forEach((element) => {
console.log(element)
numCallbackRuns++
})
console.log("numCallbackRuns: ", numCallbackRuns)
// 1
// 3
// 7
// numCallbackRuns: 3
// comment: as you can see the missing value between 3 and 7 didn't invoke callback function.