Determine Which Promise Is Slowest In Promises.all

I have been using Promise.all in my app. For the purpose of improving app speed, how to determine which promise is the slowest? const result = await Promise.all([ this.

Solution 1:

You can use a helper function for that:

asyncfunctiontime(p, name) {
    const start = Date.now();
    try {
        returnawait p;
    } finally {
        const end = Date.now();
        console.log(`${name} took ${end-start}ms`);
    }
}

Then write

const result = await Promise.all([
    time(this.props.fetchUser(), "user"),
    time(this.props.cacheResourcesAsync(), "cacheResources"),
    time(this.props.initAmplitude(), "amplitude"),
    time(this.props.initAppVariables(), "appVars"),
]);

Solution 2:

I'd do something like this :

let startTime = newDate();
Promise.all([
  this.fetchUser().then(() => { 
    console.log('fetch user takes', newDate().getTime()-startTime.getTime());
    returnarguments;}),
  this.fetchData().then(() => {
    console.log('fetchData takes', newDate().getTime()-startTime.getTime());
    returnarguments;})
]);