Iterate over a sequence of promises.

The Waterfall will resolve a list of Promises in a waterfall, passing the output of a Promise to the next one. It takes as input a list of functions that must return a Promise. The input functions will have as argument the resolved output of the previous Promise. A initial void function must be provided.

var promises=   [()=>{
        return new Promise((r,_) => r(0))
    }   ].concat([...new Array(3).keys()].map((item,index) => (res)=>{
        res++;
        return new Promise((r,_) => r(res))
    }
))
Waterfall(promises) .then(res=> console.log(res)) .catch((err) => console.error(err) );

The argument of Sequence are a list of input objects and a callback. The input callback must return a Promise. The input objects will be passed to the callback. The Sequence will resolved when all callbacks have been sequentially called on the input objects.

Sequence([...new Array(3).keys()], (res) => new Promise((r,_) => r(res++)) ).then(res => console.log(res))

Inspired to and based on promise-waterfall