Question

我有一个预先存在的JavaScript函数，它返回一个promise。我称之为

function on_success(result){
  //process result
}
foo(params).then(on_success)

我想编写包装函数bar，它将调用foo并测量执行时间。我想以完全相同的方式打电话给吧：

bar(params).then(on_success)

我这样做吗？

这是我写完的内容。它是@Sidney答案的简化版本

function bar(params){
    var start_time=new Date().getTime()
    function print_time(x){
        var end_time=new Date().getTime()
        console.log(end_time-start_time)
        return x
    }
    return foo(params).then(print_time)
}

Answer 1

如果我理解你的问题，你正在寻找这样的事情：

LatLngBounds bounds1 = new LatLngBounds(new LatLng(8.2,48.2), new LatLng(8.1,47.2));
LatLngBounds bounds2 = new LatLngBounds(new LatLng(8.1,48.1), new LatLng(8.0,47.1));
LatLngBounds.Builder boundsBuilder = new LatLngBounds.Builder();

boundsBuilder.include(bounds1.northeast);
boundsBuilder.include(bounds1.southwest);

boundsBuilder.include(bounds2.northeast);
boundsBuilder.include(bounds2.southwest);

LatLngBounds unionBounds = boundsBuilder.build();

Answer 2

你可以处理一个履行的承诺，在你的情况下停止测量，然后传递then的返回值，这本身就是一个承诺：

function measure (measuredFunction) {
    startMeasurement()

    return measuredFunction()
        .then(stopMeasurement)
}

measure(() => foo(params)).then(on_success)

Answer 3

你可以做到最基本，最不花哨的方式......

var timer = new Date().getTime();

function foo(){
  return new Promise(done=>{
    setTimeout(done, 1000);
  })
}

function on_success(result){
  //process result
  alert("it took "+(new Date().getTime() - timer)+"ms to do that...")
}

let params = {}

foo(params).then(on_success)

如何编写JavaScript promise装饰器

3 个答案: