Execute a promise list, n at time

promise_all_step.js

/* Execute a promise list, n at time */
Promise.prototype.allStep = (promiseList, n) => {
	let promises = [];
	
	for (let i = 0; i < promiseList.length; i+=n) {
		promises.push (new Promise ((resolve, reject) => {
			var p = promiseList.slice (i, i+n ? i+n <= promiseList.length : promiseList.length);

			Promise.all (p).then ((r) => {
				resolve (r);							
			});
		});
	}
	
	return new Promise ((resolve, reject) => {
		Promise.all (promises).then ((r) => {
			var rr = []
			for (let i = 0; i < r.length; i++) {
				rr = rr.concat (r[i]);
			}
			
			resolve (rr);
		});
	});
};