with closure.js

function foo(){
    return Promise.resolve('resuelta')
}

for (var i=0; i<10; i++) {

    (function(){
        var index = i;
        foo().then(function(){
            console.log(index)
        })
    })()
}

without closure.js

function foo(){
    return Promise.resolve('resuelta')
}

for (var i=0; i<10; i++) {
    foo().then(function(){
        console.log(i)
    })
}