Tutorial

Every variable in JavaScript is casted automatically so any operator between two variables will always give some kind of result.

The addition operator

The + (addition) operator is used for both addition and concatenation of strings.

For example, adding two variables is easy:

var a = 1;
var b = 2;
var c = a + b;     // c is now equal to 3

The addition operator is used for concatenating strings to strings, strings to numbers, and numbers to strings:

var name = "John";
console.log("Hello " + name + "!");
console.log("The meaning of life is " + 42);
console.log(42 + " is the meaning of life");

JavaScript behaves differently when you are trying to combine two operands of different types. The default primitive value is a string, so when you try to add a number to a string, JavaScript will transform the number to a string before the concatenation.

console.log(1 + "1");   // outputs "11"

Mathematical operators

To subtract, multiply and divide two numbers, use the minus (-), asterisk (*) and slash (/) signs.

console.log(3 - 5);     // outputs -2
console.log(3 * 5);     // outputs 15
console.log(3 / 5);     // outputs 0.6

Advanced mathematical operators

JavaScript supports the modulus operator (%) which calculates the remainder of a division operation.

console.log(5 % 3);     // outputs 2

JavaScript also supports combined assignment and operation operators. So, instead of typing myNumber = myNumber / 2, you can type myNumber /= 2. Here is a list of all these operators:

  • /=
  • *=
  • -=
  • +=
  • %=

JavaScript also has a Math module which contains more advanced functions:

  • Math.abs calculates the absolute value of a number
  • Math.exp calculates e to the power of a number
  • Math.pow(x,y) calculates the result of x to the power of y
  • Math.floor removes the fraction part from a number
  • Math.random() will give a random number x where 0<=x<1

And many more mathematical functions.

Exercise

In this exercise, you do the following:

  1. Connect the firstName and lastName to construct the variable fullName, but with a space (" ") in between the first and last name.
  2. Multiply the variable myNumber by 2 and put the result in meaningOfLife.

Tutorial Code

var firstName = “John”; var lastName = “Smith”; var myNumber = 21;

// TODO: change the following code var fullName = null; var meaningOfLife = null;

console.log(“The name is “ + fullName); console.log(“The meaning of life is “ + meaningOfLife);

Expected Output

The name is John Smith The meaning of life is 42

Solution

var firstName = “John”; var lastName = “Smith”; var myNumber = 21;

// TODO: change the following code var fullName = firstName + “ “ + lastName; var meaningOfLife = myNumber * 2;

console.log(“The name is “ + fullName); console.log(“The meaning of life is “ + meaningOfLife);