The Pragmatic Programmer

What (() => {})(); Actually Means

Written by

fire_horse

in

The code snippet is:

(() => {})();

This is an Immediately Invoked Function Expression (IIFE) in JavaScript.

Breakdown:

  • () around the function turns it into an expression
  • => {} is an arrow function
  • The final () immediately executes it
  • ; ends the statement

Equivalent older syntax:

(function() {
  // code here
})();

People used IIFEs heavily before modern module systems to:

  • avoid polluting the global scope
  • create private variables
  • execute setup code immediately

Example:

(() => {
  const secret = "hidden";
  console.log("Runs immediately");
})();

The tweet is basically joking that many “AI-assisted/vibe coders” can generate apps but may not recognize classic JavaScript patterns from interviews or legacy codebases.

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