Website Performance audit script

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SEO Help and Tips

Website Performance audit script Code

The code provided appears to be a part of a performance audit script for evaluating the server response time of a website. When this code is incorporated into a larger application or tool, such as Lighthouse, it can be used to analyze the performance of a web page.

The impact on a website depends on how this code is used and integrated within the website's infrastructure. Here are a few potential effects:

Performance Analysis: 
The code runs performance audits on the website, specifically evaluating the server response time for the main document. The results of the audit can provide insights into the website's performance and identify areas for improvement.

User Experience: 
If the server response time is slow, it can negatively impact the user experience. Users may experience delays in loading the web page, leading to frustration and potential abandonment. By optimizing the server response time based on the audit results, the website's performance and user experience can be enhanced.

Optimization Opportunities: 
The audit results provide details on the server response time, including opportunities for improvement. Developers can use this information to identify performance bottlenecks and optimize the server-side code, infrastructure, or network configurations to reduce the response time and improve overall performance.

SEO Impact: 
Website performance, including server response time, is a factor that search engines consider when ranking pages. Slow response times can affect the website's search engine optimization (SEO) and visibility in search results. By addressing performance issues identified by the audit, the website's SEO can be positively impacted.

It's important to note that the code provided is just a part of a larger performance analysis framework. Its impact on the website will be realized when integrated into the appropriate tools and processes and when the audit results are used to drive performance improvements.

"" <body>
import { Audit } from './audit.js';
import * as i18n from '../lib/i18n/i18n.js';
import { MainResource } from '../computed/main-resource.js';

const UIStrings = { title: 'Initial server response time was short', failureTitle: 'Reduce initial server response time', description: 'Keep the server response time for the main document short because all other requests depend on it. [Learn more about the Time to First Byte metric](https://developer.chrome.com/docs/lighthouse/performance/time-to-first-byte/).', displayValue: `Root document took {timeInMs, number, milliseconds}\xa0ms` };

const str_ = i18n.createIcuMessageFn(import.meta.url, UIStrings);

const TOO_SLOW_THRESHOLD_MS = 600;
const TARGET_MS = 100;

class ServerResponseTime extends Audit {
  static get meta() {
    return { id: 'server-response-time', title: str_(UIStrings.title), failureTitle: str_(UIStrings.failureTitle), description: str_(UIStrings.description), supportedModes: ['navigation'], requiredArtifacts: ['devtoolsLogs', 'URL', 'GatherContext'] };
  }

  static calculateResponseTime(record) {
    if (global.isLightrider && record.lrStatistics) return record.lrStatistics.requestMs;
    if (!record.timing) return null;
    return record.timing.receiveHeadersStart - record.timing.sendEnd;
  }

  static async audit(artifacts, context) {
    const devtoolsLog = artifacts.devtoolsLogs[Audit.DEFAULT_PASS];
    const mainResource = await MainResource.request({ devtoolsLog, URL: artifacts.URL }, context);

    const responseTime = ServerResponseTime.calculateResponseTime(mainResource);
    if (responseTime === null) {
      throw new Error('no timing found for main resource');
    }

    const passed = responseTime < TOO_SLOW_THRESHOLD_MS;
    const displayValue = str_(UIStrings.displayValue, { timeInMs: responseTime });

    const headings = [{ key: 'url', valueType: 'url', label: str_(i18n.UIStrings.columnURL) }, { key: 'responseTime', valueType: 'timespanMs', label: str_(i18n.UIStrings.columnTimeSpent) }];
    const overallSavingsMs = Math.max(responseTime - TARGET_MS, 0);
    const details = Audit.makeOpportunityDetails(headings, [{ url: mainResource.url, responseTime }], { overallSavingsMs });

    return {
      numericValue: responseTime,
      numericUnit: 'millisecond',
      score: Number(passed),
      displayValue,
      details,
      metricSavings: {
        FCP: overallSavingsMs,
        LCP: overallSavingsMs,
      },
    };
  }
}

export default ServerResponseTime;
export { UIStrings };
</body>
""

How it Works ?

It defines a class ServerResponseTime that extends an Audit class. Here's a breakdown of the code:

Import Statements: The script imports the Audit class from a file called "audit.js", the i18n module from a file called "i18n.js", and the MainResource class from a file called "main-resource.js".

UIStrings Object: The script defines an object called UIStrings that contains localized strings used for displaying titles, descriptions, and display values. These strings are intended for internationalization purposes.

STR_ Function: The script declares a str_ function that is used to retrieve localized strings based on a URL. It utilizes the i18n module and the UIStrings object to retrieve the appropriate string for a given key.

Constants: The script defines two constants: TOO_SLOW_THRESHOLD_MS and TARGET_MS. These constants are used to set the threshold values for server response time. A response time greater than TOO_SLOW_THRESHOLD_MS indicates a failure, while a response time less than TARGET_MS is considered ideal.

ServerResponseTime Class: This class is the main component of the script and represents an audit for measuring server response time. It includes a static meta method that returns metadata about the audit, such as its ID, titles, descriptions, and required artifacts.

CalculateResponseTime Method: This static method calculates the server response time based on a network request record. It checks if the record object has timing information and calculates the response time by subtracting the send end time from the receive headers start time. If the record object does not have timing information, it returns null.

Audit Method: This static method performs the actual audit. It takes in artifacts and context as parameters, retrieves the devtoolsLog and URL from the artifacts, and then calls the MainResource.request method to obtain the main resource network request information. It calculates the response time using the calculateResponseTime method, checks if it meets the threshold criteria, and generates the audit result object containing numeric values, display values, details, and metric savings.

Export Statements: The script exports the ServerResponseTime class as the default export and exports the UIStrings object as a named export.

Overall, this script defines an audit for evaluating the server response time of a website's main document and provides a framework for conducting performance analyses based on the audit results.

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