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Latest version on npm Project license

An easy way to calculate the 'impact' of running a task in Node.JS
Coded with by Simone Primarosa.


Sympact runs a script and profiles its execution time, CPU usage, and memory usage. Sympact then returns an execution report containing the averages of the results.

Do you believe that this is useful? Has it saved you time? Or maybe you simply like it?
If so, show your appreciation with a Star .

How it works

sympact spawns a separate process and runs your script in an isolated node process and then collects statistics about the system's resource used by your script.

The data are collected using pidusage in combination with pidtree.
The main difference between other projects is that sympact will also "profile" processes spawned by your script or by any of its children.

Finally a report of the samples taken is computed and returned to you.


npm install --save sympact


const impact = require('sympact');

const report = await impact(`
  let r = 2;
  let c = 10e7;
  while (c--) r = Math.pow(r, r);
  return r;
`, {interval: 125}); // 125 ms of sampling rate

console.log(report.times.execution.end - report.times.execution.start);
// => 2700 ms
// => 90.45 % on my machine
// => 27903317.33 bytes on my machine


sympact CLI

To make it more usable, a CLI is bundled with the package allowing for an aesthetically pleasing report.

  npx sympact "console.log('Hello World')"

You can even require other files.

  npx sympact "
    const {spawn} = require('child_process');
    let childno = 10;
    let childs = [];
    for (let i = 0; i < childno; i++) {
      childs.push(spawn('node', ['-e', 'setInterval(()=>{let c=10e3;while(c--);},10)']));
    let c = 10e6;
    let m = {};
    while (c--)  m[c] = c;
    for (let i = 0; i < childno; i++) {

Report object

The object returned by the promise will look like this.

  "times": {
    "sampling": {
      "start": 1521666020917,          // ms since epoch
      "end": 1521666036041             // ms since epoch
    "execution": {
      "start": 1521666020958,          // ms since epoch
      "end": 1521666036006             // ms since epoch
  "stats": {
    "cpu": {                           // CPU usage statistics (percentage)
      "mean": 74.17368421052636,
      "median": 75.1,
      "stdev": 11.820700343128212,
      "max": 94.7,
      "min": 0.7
    "memory": {                        // RAM usage statistics (bytes)
      "mean": 1080202186.1052632,
      "median": 1327509504,
      "stdev": 416083837.44653314,
      "max": 1327513600,
      "min": 23441408
  "samples": {                         // List of all the samples taken
    "period": 125,                     // Sampling period
    "count": 114,                      // Number of samples taken
    "list": {
      "39": {                          // Taken after 39ms after the start of the watch command
        "cpu": 0.7,                    // Sum of the usages of all the processes
        "memory": 23441408,            // Sum of the memory of all the processes
        "processes": [{                // List of processes profiled in this timeframe
          "cpu": 0.7,
          "memory": 23441408,
          "ppid": 837,
          "pid": 839,
          "ctime": 6000,
          "elapsed": 1000,
          "timestamp": 1521666020955   // ms since epoch
      "205": {
        "cpu": 14.8,
        "memory": 55685120,
        "processes": [{
          "cpu": 14.8,
          "memory": 55685120,
          "ppid": 837,
          "pid": 839,
          "ctime": 15000,
          "elapsed": 2000,
          "timestamp": 1521666021122


      "15124": {
        "cpu": 81.2,
        "memory": 878133248,
        "processes": [{
          "cpu": 81.2,
          "memory": 878133248,
          "ppid": 837,
          "pid": 839,
          "ctime": 47600,
          "elapsed": 17000,
          "timestamp": 1521666036041


sympact(code, [options]) Promise.<Object>

Measures the impact of running a certain script on your system. Monitors the cpu and memory usage of the whole tree of processes generated by the script provided.

Kind: global function
Returns: Promise.<Object> - An object containing the results.
Access: public

Param Type Default Description
code string The source code to test.
[options] Object Optional configurations.
[options.interval] number 125 Sampling interval in milliseconds.
[options.cwd] string "caller path" CWD for the script.


Contributions are REALLY welcome and if you find a security flaw in this code, PLEASE report it.
Please check the contributing guidelines for more details. Thanks!


See also the list of contributors who participated in this project.


This project is licensed under the MIT License - see the license file for details.

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