Variables are like little liars. They tell you exactly what you want to hear, but sometimes they tell you exactly the opposite. They're like the politician's best friend. "I'll do this, I'll do that, but really, I'll just do what I want."
Take, for example, the variable x. On a Monday, it's x=5. On a Tuesday, it's x=3. On a Wednesday, it's x=2. You get the idea. Don't ask me why, just don't ask me why.
But wait, there's more! y is even worse. On a Thursday, it's y=7. On a Friday, it's y=1. On a Saturday, it's y="Hello World!". On a Sunday, it's y=0. Don't ask me why, just don't ask me why.
var x = 5; // Monday
x = 3; // Tuesday
x = 2; // Wednesday
var y = 7; // Thursday
y = 1; // Friday
y = "Hello World!"; // Saturday
y = 0; // Sunday