JavaScript - 如何测量代码每个部分的执行时间

Question

用于连接数据库和获取数据的 JS 代码如下。

我可以使用node db.js命令在终端中运行整个代码并测量总执行时间，但我想测量每个代码块执行所需的时间（以毫秒为单位）：

# Part 1:
var mysql = require('mysql');

# Part 2:
var connection = mysql.createConnection({
    host: '...',
    user: '...',
    password: '...'
    port : ...
    database: '...'
});

# Part 3:
connection.connect(function(err) {
  if (err) throw err;
  connection.query("SELECT * FROM table", function (err, result, fields) {
    if (err) throw err;
    console.log(result);
  });
  connection.end();
});

如何测量上面的每个部分？

谢谢。

Answer 1

您可以使用console.time('name')和console.timeEnd('name')来测量代码中两个位置之间的时间。

看起来像这样：

console.time('part1')   //start timer for part 1.
var mysql = require('mysql');
console.timeEnd('part1')    //end timer 1 and log how long it took.  

console.time('part2')   //start timer for part 2.
var connection = mysql.createConnection({
    host: '...',
    user: '...',
    password: '...'
    port : ...
    database: '...'
});
console.timeEnd('part2')    //end timer 2 and log how long it took. 

console.time('part3')   //start timer for part 3.
connection.connect(function(err) {
  if (err) throw err;
  connection.query("SELECT * FROM table", function (err, result, fields) {
    if (err) throw err;
    console.log(result);
    console.timeEnd('part3')    //end timer 3 in the callback and log how long it took. 
  });
  connection.end();
});

Answer 2

使用console.time(String str)启动一个命名计时器，并使用console.timeEnd(String str)结束测量并在控制台中输出时间。

 function countToThousand(callback) { console.time('part1'); let a = 0; for (var i = 0; i < 1000; i++) { a += i } callback(a) } function myCallback(a) { console.log('a is '+a); console.timeEnd('part1') } countToThousand(myCallback) // etc 

Answer 3

如果您的问题实际上是“如何知道代码的哪一部分是sloooow”。 做这种事情的工具称为“探查器”。

NodeJS具有集成的探查器，可以将其附加到您的IDE（例如Inteliji Webstorm ）

或者，您可以搜索连接到V8探查器的专用软件包（例如v8-profiler ），并绘制图表/用其他一些软件包/自己的代码填充表格。

Answer 4

您可以使用内置的nodejs perf_hooks。 例如：

// Dependencies
const { performance, PerformanceObserver } = require('perf_hooks');



performance.mark('start part1');
console.time('part1')   //start timer for part 1.
var mysql = require('mysql');
console.timeEnd('part1')    //end timer 1 and log how long it took.  
performance.mark('end part1');

performance.mark('start part2');
console.time('part2')   //start timer for part 2.
var connection = mysql.createConnection({
  host: '...',
  user: '...',
  password: '...'
    port: ...
  database: '...'
});
console.timeEnd('part2')    //end timer 2 and log how long it took. 
performance.mark('end part2');

performance.mark('start part3');
console.time('part3')   //start timer for part 3.
connection.connect(function (err) {
  if (err) throw err;
  connection.query("SELECT * FROM table", function (err, result, fields) {
    if (err) throw err;
    console.log(result);
    console.timeEnd('part3')    //end timer 3 in the callback and log how long it took. 
    performance.mark('end part3');

    // Create observer to log out all the measurements
    const obs = new PerformanceObserver((list) => {
      // called once. list contains three items
      const measurements = list.getEntriesByType('measure');
      measurements.forEach((measurement) => {
        console.log(`${measurement.name} ${measurement.duration}`);
      });
    });
    obs.observe({ entryTypes: ['measure'] });

    // Gather all the measurements
    performance.measure('Beggining to end', 'start part1', 'end part3'); // Measure whole function
    performance.measure('Part1', 'start part1', 'end part1'); // Measure the part1
    performance.measure('Part2', 'start part2', 'end part2'); // Measure the part2
    performance.measure('Part3', 'start part3', 'end part3'); // Measure the part3

  });
  connection.end();
});

Answer 5

使用这个方法

 const startTime =new Date().getTime();

//part of the code

const endTime = new Date().getTime();
console.log(`time taken=> ${(endTime - startTime)/1000} seconds`);