问chromedp -如何从控制台检索FCP等

EN

package main

import (
    "context"
    "encoding/json"
    "log"

    "github.com/chromedp/chromedp"
)

type performancePaintTiming struct {
    EntryType string  `json:"entryType"`
    Name      string  `json:"name"`
    Duration  int     `json:"duration"`
    StartTime float64 `json:"startTime"`
}

func main() {
    ctx, cancel := chromedp.NewContext(context.Background(),
        // Enable the debug mode to see the CDP messages.
        // It's helpful to understand how CDP works.
        // But please don't enable it in Production Environment.
        chromedp.WithDebugf(log.Printf))
    defer cancel()

    // I don't know why but it seems that Runtime.evaluate does not return
    // JSON object any more, so I have to stringified it into a string.
    js := `
const paintTimings = performance.getEntriesByType('paint');
const fcp = paintTimings.find(({ name }) => name === "first-contentful-paint");
JSON.stringify(fcp);`

    var res string
    if err := chromedp.Run(ctx,
        chromedp.Navigate("https://www.bing.com/"),
        chromedp.EvaluateAsDevTools(js, &res),
    ); err != nil {
        panic(err)
    }

    var fcp performancePaintTiming
    if err := json.Unmarshal([]byte(res), &fcp); err != nil {
        panic(err)
    }

    log.Printf("%#v", fcp)
}