Question

我一直在我的应用中使用Promise.all。为了提高应用程序速度，如何确定哪个承诺最慢？

const result = await Promise.all([
          this.props.fetchUser(),
          this.props.cacheResourcesAsync(),
          this.props.initAmplitude(),
          this.props.initAppVariables(),
        ]);

Answer 1

您可以使用辅助函数：

async function time(p, name) {
    const start = Date.now();
    try {
        return await p;
    } finally {
        const end = Date.now();
        console.log(`${name} took ${end-start}ms`);
    }
}

然后写

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"),
]);

Answer 2

我会做这样的事情：

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

确定Promises.all中哪个承诺最慢

2 个答案: