This document discusses JavaScript closures using the example of a careless citizen who loses their credit card to a thieving punk. An inner function called thievingPunk() is able to access and modify the outer function's card variable, demonstrating how closures allow inner functions to access variables in an enclosing scope. The document then provides instructions for recreating the credit card theft example in a browser debugger to see closures in action.

1. JavaScript Closures
The Story of the Lost Credit Card
A closure is formed when an inner function gets its hands on
free variables (by reference that is).
http://tech.pro/tutorial/1744/javascript-closures-or-the-story-of-the-lost-credit-card

2. The Happening
function carelessCitizen() {
var card = 3000;
function thievingPunk() {
card = card - 1500;
}
thievingPunk();
}
carelessCitizen();

3. Set up the CCTV
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Fire up Google Chrome
Press F12
Go to Sources, Snippets
Right click, choose New
Name it card.js
Write debugger;
Add the rest of the code

4. Caught in The Act
Frame 1
Press F11

5. Caught in The Act
Frame 5
TED !!!
BUS

6. Dumitru Ungureanu
itmitica@gmail.com