Execute all promises in a chain.

gistfile1.js

var a = new Promise(res => setTimeout(()=>{ 
          res(1)
        }, 2000));

var b = new Promise(res => setTimeout(()=>{    
          res(2)
        }, 1000));

var c = (fn) => new Promise(res => console.log(fn)); 

var arr = [a, b];
arr.reduce(function(promise, next) {
    return promise.then(_ => next).then( value => {
        console.log(value); // ***
        return value;
    });
}, Promise.resolve());
// => 1, 2

//hardcode
a.then(r1 => r1.then(c(r1).then(b.then(r2 => r2.then(c(r2))))))
// => 1, 2