ESlint on Nvim is not linting syntax error

Question

I am using coc-eslint on NeoVim with the following config and I am not getting proper linting on very basic error.

.eslintrc.json

{
    "env": {
        "browser": true,
        "es2021": true
    },
    "extends": "eslint:recommended",
    "overrides": [
    ],
    "parserOptions": {
        "ecmaVersion": "latest"
    },
    "rules": {
    }
}

Example of errors:

        var mapTargetX = Math.floor((playerY / MAP_SCALE)) * MAP_SIZE + Math.floor((playerX + playerOffsetX) / MAP_SCALE);
        var mapTargetX = Math.floor((playerY + mapOffsetY) / MAP_SCALE) * MAP_SIZE + Math.floor((playerX / MAP_SCALE)); //Here I redeclare the same variable.

    document.onKeyDown = function(event) { //Here I used camelcasing when I shouldn't.
        ... }

Solution I have tried:

• 'use strict' This doesn't seem to change anything.
• Check the errors in the dev tools console window of the browser, sadly no error.
• Added the following rule to fix the redeclare linting error :

 "rules": {
   "no-redeclare": "error"
 }

This also didn't fix the problem.