Using a variable

var number1 = 5;
number1 = 3;

Here, we defined a number called “number1” which was equal to 5. However, on the second line, we changed the value to 3. To show the value of a variable, we log it to the console or use window.alert():

console.log(number1); // 3
window.alert(number1); // 3

To add, subtract, multiply, divide, etc., we do like so:

number1 = number1 + 5; // 3 + 5 = 8
number1 = number1 - 6; // 8 - 6 = 2
var number2 = number1 * 10; // 2 (times) 10 = 20
var number3 = number2 / number1; // 20 (divided by) 2 = 10;

We can also add strings which will concatenate them, or put them together. For example:

var myString = "I am a " + "string!"; // "I am a string!"