TypeScript (and, for ES2015 and above, JavaScript) port of Python's `enumerate` to make index-value pairs.

enumerate.ts

/**
 * Generates `[index, value]` 2-tuples, so you can `for (let [index, value] of enumerate(v) {...})`.
 * @param v array or iterable iterator to enumerate
 * @param n starting number (defaults to 0)
 * 
 * Hat tip: https://docs.python.org/3/library/functions.html#enumerate
 */
export function* enumerate<T>(v: T[]|IterableIterator<T>, n: number = 0): IterableIterator<[number, T]> {
  for (let x of v) { yield [n++, x]; }
}