Simple example of Javascript variable hoisting

hoisting-loop.js

// Demonstration of how easy it is for this to mess up your loops.

var txt = ["a","b","c"];

for (var i = 0; i < 3; ++i ) { 
   var msg = txt[i];
    setTimeout(function() { alert(msg); }, i*1000);        
}​

// Alerts 'c', 'c', 'c'

hoisting.js

// Simple demonstration of function scope.

var n = 1;

function printSomething() {
    console.log(n);
    var n = 2;
    console.log(n);
}

=> printSomething();
undefined
2

no-hoisting-loop.js

// Pattern to avoid that by binding to variable in another function.

var txt = ["a","b","c"];

for (var i = 0; i < 3; ++i ) {    
    setTimeout((function(msg) { 
      return function() { alert(msg); } 
    })(txt[i]), i*1000);        
}​

// Alerts 'a','b','c'