JavaScript - Execution Context & Lexical Scope

Overview

Estimated time: 10–15 minutes

Execution context and lexical scope determine how variables and functions are resolved in JavaScript.

Learning Objectives

• Understand the call stack and execution context.
• Know how lexical scope affects variable resolution.

Prerequisites

• JavaScript - Engine & Runtime

Execution Context

function foo() {
  var a = 1;
  function bar() {
    console.log(a);
  }
  bar();
}
foo();

Lexical Scope

function outer() {
  var x = 10;
  function inner() {
    console.log(x);
  }
  return inner;
}
const fn = outer();
fn();

Common Pitfalls

• Confusing dynamic scope (not used in JS) with lexical scope.

Summary

Understanding execution context and lexical scope is key to mastering closures and advanced JS patterns.