Scope & Closures

Scope

Global — everywhere
Function — inside function
Block — inside {} (let/const)

Closure

A function remembers variables from its outer scope even after that scope is gone.

Example

function makeCounter(){
  let count=0;  // private
  return {
    inc:()=>++count,
    dec:()=>--count,
    val:()=>count
  };
}
const c=makeCounter();
c.inc(); c.inc();
console.log(c.val()); // 2

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Related Resources

JavaScript Reference

Complete tag & property list

JavaScript How-To Guides

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JavaScript Exercises

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