Using Promise.all on the entries of a Map()

Question

I am using a Map for some key/value pairs

let myMap = new Map()
myMap.set('foo', 'bar')
myMap.set('foo2', 'bar42')

For every Map entry I execute a function which returns a Promise. All these Promises can be executed in parallel using Promise.all.

This is how I do it right now:

let mapPromises = []
myMap.forEach((value, key) => {
  mapPromises.push(MyModel.forge({key, language, value}).save())
})
await Promise.all(mapPromises)

Is there another (shorter?, faster?) approach to accomplish this than pushing all function calls into an array and then triggering Promise.all?

Answer 1

The simplest code I could come up with is

await Promise.all(Array.from(myMap, ([key, value]) => 
    MyModel.forge({key, language, value}).save())
);

See Array#from documentation

Answer 2

Yes, using forEach and manually pushing to an array is almost always a bad idea.

You can directly create the array from the map, mapping over it in the process:

async function processEntry([key, value]) {
    return MyModel.forge({key, value}).save();
}

(async function() {
    let myMap = new Map()
    myMap.set('foo', 'bar')
    myMap.set('foo2', 'bar42')

    const results = await Promise.all(Array.from(myMap, processEntry));
}());

But if you want to use an iterator, you also can do something like

function* processEntries(map) {
    for (const [key, value] of map)
        yield MyModel.forge({key, value}).save();
}

(async function() {
    let myMap = new Map()
    myMap.set('foo', 'bar')
    myMap.set('foo2', 'bar42')

    const results = await Promise.all(processEntries(myMap));
}());