Any variable or function declared in the global scope implicitly becomes attached to the global object (the window object in a browser environment). To make it explicit this variable or function should be a property of window. When it is meant to be used just locally, it should be declared with the const or let keywords (since ECMAScript 2015) or within an Immediately-Invoked Function Expression (IIFE).

This rule should not be activated when modules are used.

Noncompliant Code Example

var myVar = 42;       // Noncompliant
function myFunc() { } // Noncompliant

Compliant Solution

window.myVar = 42;
window.myFunc = function() { };

or

let myVar = 42;
let myFunc = function() { }

or

// IIFE
(function() {
  var myVar = 42;
  function myFunc() { }
})();