Basic Maths Functions JS Home  <<  JS Basics  <<  Basic Maths Functions

In this lesson we look at some of the basic maths and assignment operators. Basic mathematical operations are supported in JavaScript using symbols as follows:

  • Addition uses the + symbol as in 10 + 10
  • Subtraction uses the - symbol as in 10 - 10
  • Division uses the / symbol as in 10 / 10
  • Multiplication uses the * symbol as in 10 * 10
  • Modulus uses the % symbol as in 17 % 5

You can also assign numbers to variables and apply maths to them.


// Create some variables and add them together.
var firstNumber = 10;
var secondNumber = 10;
alert(firstNumber + secondNumber);

Press the button below to action the above code:

Operation Order.

There are certain rules to follow when performing several mathematical operations in the same statement.

  • Use parentheses to group operations you want performed first.
  • Orders (also known as indices and exponents) which are powers and square roots etc. are appplied next.
  • Division and Multiplication take precedence over Addition and Subtraction.
  • After these precedences are applied maths is worked out from left to right.


/*
 * No Parentheses so multiplication will be done first.
 * Result is 32 not 50
 */ 
alert(2 + 3 * 10) + ' NO Parentheses so multiplication will be done first'; 

// Parentheses will be done first.
alert((2 + 3) * 10) + ' Maths in Parentheses will be done first';

Press the button below to action the above code:

Maths Shortcut Assignments For Variables


There are several shortcuts available when performing maths on a variable.

  • += will add the value on the right of the equal sign to the variable of the left.
  • -= will subtract the value on the right of the equal sign from the variable on the left.
  • *= will multiply the value on the right of the equal sign by the variable on the left.
  • /= Divides the variable by value on the right of the equal sign.
  • ++ Placed after a variable will add 1 to the variable.
  • -- Placed after a variable will subtract 1 from the variable.


aTotal = 0;
aTotal = aTotal + 10;
aTotal += 10; // Same as above 

aTotal = aTotal * 10;
aTotal *= 10; // Same as above 

aTotal = 0;
aTotal++; // aTotal equals 1

Lesson 5 Complete

In this lesson we looked at some of the basic mathematical functions, precedence and assignment shortcuts.

All the arithmetic operators are discussed in JavaScript Reference - Arithmetic Operators and the assignment operators are discussed in JavaScript Reference - Assignment Operators. So any operators not covered here will be discussed in those references.

Related Tutorials

JavaScript Intermediate Tutorials - Lesson 6 - More Maths Functions
JavaScript Advanced Tutorials - Lesson 3 - Number
JavaScript Advanced Tutorials - Lesson 4 - Math

Reference

JavaScript Reference - Arithmetic operators
JavaScript Reference - Assignment operators