Here's a function eachWithIndex that works with anything iterable.
You could also write a similar function eachWithKey that works with objets using for...in.
// example generator (returns an iterator that can only be iterated once)
function* eachFromTo(start, end) { for (let i = start; i <= end; i++) yield i }
// convers an iterable to an array (potential infinite loop)
function eachToArray(iterable) {
const result = []
for (const val of iterable) result.push(val)
return result
}
// yields every value and index of an iterable (array, generator, ...)
function* eachWithIndex(iterable) {
const shared = new Array(2)
shared[1] = 0
for (shared[0] of iterable) {
yield shared
shared[1]++
}
}
console.log('iterate values and indexes from a generator')
for (const [val, i] of eachWithIndex(eachFromTo(10, 13))) console.log(val, i)
console.log('create an array')
const anArray = eachToArray(eachFromTo(10, 13))
console.log(anArray)
console.log('iterate values and indexes from an array')
for (const [val, i] of eachWithIndex(anArray)) console.log(val, i)
The good thing with generators is that they are lazy and can take another generator's result as an argument.