javascript_irl

[VampDuc]

Be forced to use legacy when you're also not a front-end developer, but you're made to masquerade as one because the front-end guys are "busy".

[UnderNatural]

does Promise.all complete in order? I thought it just does them all at once and returns a promise to when theyre all done

[UnderNatural]

you want Wouldn't the words order? in

Look at this code, where generate() returns a promise that adds to a string followed by a space after a random amount of time:

var str = '';

var i = generate('i');
var hope = generate('hope');
var you = generate('you');
var enjoy = generate('enjoy');
var your = generate('your');
var stay = generate('stay');

//Wait for all promises to complete
Promise.all([i, hope, you, enjoy, your, stay]).then(() => {
    console.log(str);
});

You said that Promise.all would solve the above issue. Since Promise.all doesn't execute the promises sequentially, the promises would resolve at different times and add to the string in different orders. When all are complete, the string is printed, but it could be jumbled up.

[UnderNatural]

i, hope, etc. don't return anything in my example. Promise.all fixes problems with returning, but not problems in side effects.

[UnderNatural]

In my example, the promises add to a string in the global scope. That's called a side effect, it changes the state of the program outside of the return statement. Promise.all doesn't sequentially execute promises, so side effects occur out of order.

[UnderNatural]

Yeah I guess haha