t.js

function deferredTimeout(delay) {
    var deferred = new Deferred();
    setTimeout(function() {
        deferred.callback({
            called: true
        })
    },
    delay);
    return deferred;
}

function a() {
    for (var i = 0; i < 4; ++i) {
        console.log("a"+i);
        await deferredTimeout(1000);
    }
}

function b() {
    for (var i = 0; i < 4; ++i) {
        console.log("b"+i);
        await deferredTimeout(1000);
    }
}

function main() {
	await a();
	await b();
}
var d = main().then(function () { console.log('Done!'); });