The answer
Use ES modules (import/export) to keep declarations out of window. Use IIFes in script files to contain var. Avoid var at the top level; prefer let and const.
The window Object in JavaScript Explained
How do you avoid polluting the window object?
More FAQs in The window Object in JavaScript Explained
It is the global object in browsers. It represents the browser tab and holds global variables (from var), built-in APIs (console, setTimeout, fetch), the DOM (document), and UI methods (alert, prompt).
No. Only var declarations at the top level become properties of window. let, const, and class declarations live in a separate global lexical environment and do not attach to window.
window is the global object representing the browser tab. document is the parsed HTML page inside that tab, accessible as window.document. window holds APIs and globals; document holds the DOM tree.
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