When importing functions in for example, ReactJS, I normally import only specific functions.

import { useEffect, useState, /* ETC... */ } from 'react';

But is there a difference to just importing the whole module?

import React from 'react';

Except for the fact that you'll need to do React.useState() instead of useState(), is there a difference in performance? Does it load faster etc. I know it probably reads the entire file in both cases but is anything else affected?

CodePudding user response：

It's a very good question. I have already installed the extension Import Cost from VSCode which let you know the import size cost of each library and the way you import that.

This library has a post explaining it in detail. Medium Import Cost Post

I try to test it and the result is different depending on the way you import everything or just the method. Default import Selective importing