js-string-memory-usage

index.js

// node --max-old-space-size=100  --expose-gc index.js

const prettyBytes = require('pretty-bytes');

const forceGC = () => {
    if (global.gc) {
        global.gc();
    } else {
        console.warn('No GC hook! Start your program as `node --expose-gc file.js`.');
    }
}

const memoryUsage = () => {
    forceGC();
    const used = process.memoryUsage();
    return Object.entries(used).reduce((acc, [key, value]) => `${acc}\n${key}: ${prettyBytes(value)}`, '')
}

// const randomString = () => Math.random().toString(36).substring(2, 15) + Math.random().toString(36).substring(2, 15);

const randomId = (length) => {
    var result = '';
    var characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    var charactersLength = characters.length;
    for (var i = 0; i < length; i++) {
        result += characters.charAt(Math.floor(Math.random() * charactersLength));
    }
    return result;
}


console.log('START:', memoryUsage());

let arr = [];

const allocate = () => {
    // 600,000 strings === `100 MB`
    // 600,000 numbers === '9.02 MB'
    for (var i = 0; i < 750000; i++) {
        arr.push(`${randomId(2)}-${randomId(13)}`);
    }
}

const unallocate = () => {
    arr = undefined;
}

allocate();
// unallocate();

console.log(arr);

console.log('END:', memoryUsage()); // heapUsed is the one to monitor. It will go up *and down with GC*.