run promise / task in sequence

promise-sequence.js

var tasks = [
    function(resolve) {
        return setTimeout(function() {
            console.log(1);
            resolve();
        }, 300);
    },
    function(resolve) {
        return setTimeout(function() {
            console.log(2);
            resolve();
        }, 200);

    },
    function(resolve) {
        return setTimeout(function() {
            console.log(3);
            resolve();
        }, 100);
    },
];

tasks.reduce(function(promise, task) {
    return promise.then(function() {
        return new Promise(function(res) {
            task(res);
        });
    });
}, Promise.resolve());