processConsecutive.js

function processConsecutive(list, func) {
	let len = list.length
	let i = 0

	return new Promise(resolve => {
		const iterate = item => {
			func(item, () => {
				i++

				if (i < len) {
					return iterate(list[i])
				}

				resolve()
			})
		}

		iterate(list[i])
	})
}