Variable value changes

Suppose we have a variable to which we have assigned some value. We can apply again the assignment operation then and assign an another value to this variable:

let a; // declare a variable a = 1; // assign the value 1 to it alert(a); // shows 1 a = 2; // now assign the value 2, overwriting the value 1 alert(a); // shows 2

That is, the value of a variable is not something rigidly attached to it. We can freely write some data to a variable, read it, then write something else - and so on.

Create the variable a. Assign the value 10 to it, display it on the screen. Then write the value 20 into it, display it on the screen.