js: Promise loop timeout

promise_loop_timeout.js

var p = new Promise(function(resolve, reject)
{
    resolve();
});

for(var r='', i=0; i<3; i++)
{
    (function(_i)
    {
        p = p.then(function()
        {
            return new Promise(function(resolve, reject) {
                var timeout = (_i===0)?0:1000;
                setTimeout(function()
                {
                    console.log(_i);
                    r +=  _i+" ";
                    resolve(r);
                }, timeout);
            });
        });
    })(i);
}
p.then(function(response)
{
    console.log(response);
});

/*
output:
0
1 // 1 sencod later from init
2 // 2 sencods later from init
0 1 2
*/