为什么 ESLint 对使用的未使用变量发出警告？

Question

I've been writing React & ES6 code for about 2 months now. Not sure if I just haven't ran into this problem, or if I'm having a brain freeze this morning.

Did some research and ran into a bunch of articles on const & let but nothing address this. I've been reading that you don't need to use var anymore, so then how would you handle this situation?

function () {
  let variable = null;

  if (condition) {
    variable = 'hello world';
  }

  console.log(variable); // want 'hello world' if condition
}

Edit: please assume function is being called & condition is true .

I see the code works under these conditions but my confusion is this: before I referenced the variable in the console log, my ESlint reports [eslint]: 'variable' is assigned a value but never used .

Isn't it being used?

Answer 1

By "using it", ESLint is referring to actually putting it to some use. Simply putting a value in it does not constitute using it, as far as ESLint is concerned.

A variable whose value is never accessed serves no purpose.

Answer 2

so its an eslint rule: https://eslint.org/docs/rules/no-unused-vars

if you are not familiar with what does eslint do:

Its goal is to provide a pluggable linting utility for JavaScript

if you think you wanna remove this rule you can add this line to .eslintrc

nikko:cms-v3 nikko$ cat .eslintrc.json
{
  "rules": {
    ...
    "no-unused-vars": "off", // add this

Isn't it being used?

it doesnt matter if function is called or not, if eslint sees you define a variable in that scope but you never used the variable, it will spit that error. What you did was re-defining the variable not using it.

let variable needs to be somehow consumed by some process