I'm using this method of Node.js Os module: os.freemem()

This is my sample code:

const os = require('os');

const bytesToSize = (bytes) => {
const sizes = ['Bytes', 'KB', 'MB', 'GB', 'TB'];
if (bytes == 0) return '0 Byte';
const i = parseInt(Math.floor(Math.log(bytes) / Math.log(1024)));
return Math.round(bytes / Math.pow(1024, i), 2) + ' ' + sizes[i];
};

 console.log('free memory : ', bytesToSize(os.freemem()));
 console.log('total memory : ', bytesToSize(os.totalmem()));

after I run my code, I give the below result:

free memory : 164 MB

total memory : 8 GB

but my OS system monitor show me:

Why is there such a difference?

I'm using this method of Node.js Os module: os.freemem()

This is my sample code:

const os = require('os');

const bytesToSize = (bytes) => {
const sizes = ['Bytes', 'KB', 'MB', 'GB', 'TB'];
if (bytes == 0) return '0 Byte';
const i = parseInt(Math.floor(Math.log(bytes) / Math.log(1024)));
return Math.round(bytes / Math.pow(1024, i), 2) + ' ' + sizes[i];
};

 console.log('free memory : ', bytesToSize(os.freemem()));
 console.log('total memory : ', bytesToSize(os.totalmem()));

after I run my code, I give the below result:

free memory : 164 MB

total memory : 8 GB

but my OS system monitor show me:

Why is there such a difference?

• javascript
• node.js

• you are mixing data measurement... 1 KB = 1000 bytes. 1 KiB = 1024. Your sizes array should be ['Bytes', 'KiB', 'MiB', 'GiB', 'TiB'] if you are using 1024 – Endless Commented Aug 18, 2018 at 19:33

2 Answers 2

Apparently system monitor doesn't show you the free memory, but the available one.

Node's OS.freemem() and free mand use the information from /proc/meminfo:

klaimmore@klaimmore-HP-ZBook-14:/rep$ sudo cat /proc/meminfo | grep Mem
MemTotal:       16320372 kB
MemFree:         1274072 kB
MemAvailable:   10618284 kB
klaimmore@klaimmore-HP-ZBook-14:/rep$ node -p "require('os').freemem()/1024"
1254828
klaimmore@klaimmore-HP-ZBook-14:/rep$ free -k
              total        used        free      shared  buff/cache   available
Mem:       16320372     4684776     1273228      678996    10362368    10617452
Swap:       2097148           0     2097148

Even though, it is true, and node.js returns "free" memory only, it does not make a lot of sense for macOS.

If you really need to access "available" memory, you may use the following package:

https://www.npmjs./package/osx-extra

const osX = require("osx-extra");

const freeMem = osX.freemem();

this package provides freemem() method that returns the actual available memory for macOS and fallbacks to the same freemem() methods from node:os core module for other operating systems.