Bluebird promisify vs promisifyAll Performance compare when want to promisification of one method from module

Question

I want to know performance difference between bluebird promisify vs promisifyAll.

I have tried performance test of bluebird promisify and promisifyAll.

But time and memory wise i do not see major difference, Still i thought promisify is slightly fast and less memory occupy. Still what is best.

Suppose i want Promisification of renderFile of ejs module for just 1 method renderFile.

I have 2 options

const ejs = require('ejs');
const renderFile = Promise.promisify(ejs.renderFile, {context: ejs});

or

const ejs = Promise.promisifyAll(require('ejs'));

I test performance via

console.time('A');
console.timeEnd('A');

and console.log(process.memoryUsage());

Pls answer about what should i use when i want promisification of only 1 method.

Answer 1

Which method of promisification you are using does not affect the performance of the promisified method at all.

Of course, calling promisify will do less work than calling promisifyAll, but since both would be called only once during startup of your program, it does not matter in practice.