Q.while

q-while.js

var Q = require('q')

Q.while = (conditionCallback, stepCallback) => {
	var deferredWhile = Q.defer()

	//
	// CONDITION
	//
	// This is where the condition checking happens:
	// 1) check the conditional
	// 2) notify the promise so that it can execute the body
	//
	function _whileStep() {
		return Q.fcall(conditionCallback)
		.catch(e => { deferredWhile.reject(e) })
		.then(result => {
			if (result) deferredWhile.notify()
			else deferredWhile.resolve()
		})
	}

	//
	// BODY
	//
	// This executes the body of the loop, and
	// then calls again to the 'step' function (try to iterate again)
	//
	deferredWhile.promise.progress(() => {
		Q.fcall(stepCallback)
		.catch(e => { deferredWhile.reject(e) })
		.then(() => _whileStep())
	})
	
	// start the loop:
	_whileStep()
	return deferredWhile.promise
}