JavaScript Closure Example

js-closure-example.js

function f(y) {
  var z = 1;
  return function g(y) {
    alert(y + z);
  }
}
var z=10;
f(); //returns the function: function g(y) {alert(y + z);}
f()(2); //grabs function g, assings 2 to y, knows z is 1 through closure scope and makes an alert(3)

//ANOTHER EXAMPLE

function f(y) {
  var z = 1;
  function g(y) {
    alert(y + z);
  }
  g(y);
}
var z=10;
f(2); // calls f and alerts 3, inside g JavaScript knows variabe z because it is inside a Closure Scope.