Using javascript to do math

Javascript Math Tutorial: How to do Math in Javascript

In all programming languages, performing mathematical operations is done routinely. Adding, subtracting, and many other operations are all required in any application. In Javascript, we can do this through simple operations, and by leveraging the Javascript Math object.

Note: to do mathematical operations, we need to be comparing numbers. A number that is in quotation marks will not work in mathematical operations.

Mathematical Operations

Let’s take a look at a simple mathematical operation how we can use maths in variables which we covered here. Basic maths operations work just the same as if we were to write them on paper:

Above, we have defined a variable i . We then define another variable, j , which is equal to i plus 10. Therefore, when we refer to j in our code, it will return 11.

There are a bunch of other mathematical operations we can do. Let’s take a look at them all.

Javascript Arithmetic Operators

Operator	What it does	Code example
+	Adds two numbers together	10 + 5 returns 15
—	Subtract one number from another	10 — 5 returns 5
+	Divide one number by another	10 / 5 returns 2
*	Multiply two numbers together	10 * 5 returns 50
%	Get the remainder of a calculation	12 % 5 returns 2 (12 divided by 5 leaves a remainder of 2)
**	Raises one number to the power of another	2 ** 3 returns 8 (2 to the power of 3 is 8)

let x = 12; let y = 15; let add = x + y; let remainder = x % y; let raiseToPower = x ** y; let divide = x / y; console.log("Addition: " + add); console.log("Remainder: " + remainder); console.log("To the Power: " + raiseToPower); console.log("Divide: " + divide);

Math Constants

Apart from being able to do basic maths with operators in Javascript, we also have the Math object in Javascript. This object lets us access mathematical constants and do some more complicated maths.

Let’s start by looking at Mathematical constants Below is an example of how we can access PI.

let pi = Math.PI; // returns 3.141. 

In Javascript, we use a dot to note the specific child of the Math object. These are all predefined, so they exist as part of basic Javascript. The above code will return the value PI — but most common mathematical constants are available in Javascript. These irrational numbers are all listed below, and can be used in the same way as a normal number:

Mathematical Constant	What it does	Value
Math.PI	Returns PI	3.141 .
Math.E	Returns Euler’s number	2.718 .
Math.E	Returns Euler’s number	2.718 .
Math.LN2	Returns ln(2)	0.693 .
Math.LOG10E	Returns log10(e)	0.434 .
Math.LOG2E	Returns log2(e)	1.442 .
Math.LN10	Returns ln(10)	2.302 .
Math.SQRT2	Returns the square root of 2	1.414 .
Math.SQRT1_2	Returns the square root of 1/2	0.707 .

Mathematical Notation in Javascript

If you are used to working in a mathematics environment, you will be used to scientific or mathematic notation. We can use mathematical notation in Javascript. A mathematic notation for 3124 could be written as 3.124e3.

let myMathNotation = 3.124e3 console.log(myMathNotation); 

We use e to refer to the exponent. The above is the same as writing 3.124 x 10 3 .

Rounding and Static Methods

We can use the Math object to do some more complicated mathematics, using functions that are built into it. These functions take a number as a value, and then adjust it accordingly. Let’s look at a few examples.

Abs

Math.abs takes a number and returns its absolute value. All that means, is it makes it positive if it was negative, and keeps it positive if it already was. It is the equivalent of the mathematic concept of magnitude.

let absoluteNumber = Math.abs(-2); // Returns 2. 

Floor

Math.floor takes a number and rounds it down. This will only work with decimals.

let roundItDown = Math.floor(2.8371); // Returns 2. 

Ceil

Math.ceil takes a number and rounds it up. This will only work with decimals.

let roundItDown = Math.ceil(2.8371); // Returns 3. 

Round

Math.round takes a number and rounds it. This will only work with decimals.

let roundItDown = Math.ceil(1.453); // Returns 1. 

Max

Math.max takes a set of numbers separated by commas, and picks the biggest one.

let biggestNumber = Math.max(2, 3, 6); // Returns 6. 

Min

Math.min takes a set of numbers separated by commas, and picks the smallest one.

let smallestNumber = Math.min(2, 3, 6); // Returns 2. 

More Static Methods

These useful operations let us manipulate or perform mathematical operations on numbers.

Pow

Math.pow takes a number, and raises it to a certain power. It is similar to the ** arithmetic operator we looked at earlier.

let toThePower = Math.pow(2, 3); // Returns 8, i.e. 2 to the power of 3. 

Sign

Math.sign takes a number, and returns it sign. Not to be confused with sin

let getSign = Math.sign(-14); // Returns -1 let getAnotherSign = Math.sign(14); // Returns 0 

Trunc

Math.trunc takes a number, and returns only the integer part of it.

let truncIt = Math.trunc(14.2431); // Returns 14 

Sqrt

Math.sqrt takes a number, and returns its square root.

let sqrtIt = Math.sqrt(4); // Returns 2 

Cbrt

Math.sqrt takes a number, and returns its cube root.

let cbrtIt = Math.sqrt(8); // Returns 2 

Random

Math.random returns a random number between 0 and 1.

let randomNumber = Math.random(); // As an example, may return 0.4845737088624795 

Logs

There are a number of ways to do logs in Javascript, all of which are shown below:

let naturalLog = Math.log(10); // The natural log of 10 let log10 = Math.log10(10); // The base 10 log of 10 let log2 = Math.log2(10); // The base 2 log of 10 let log2 = Math.log1p(10); // The natural log of 1 + 10 

Operations for Geometry

There are a whole host of operations we can run to manipulate and calculate geometry. A list of these geometry functions are shown below. For all of these, it is assumed that the number is in radians.

As well as the basic sin, cos and tan operations, we also have functions for the arc versions of each (denoted with an a in front of the function), and the hyperbolic versions (denoted with an h at the end).

let x = 1.4;  // Geometry mathematical functions Math.sin(x); Math.cos(x); Math.tan(x); Math.asin(x); Math.acos(x); Math.atan(x); Math.sinh(x); Math.cosh(x); Math.tanh(x); Math.asinh(x); Math.acosh(x); Math.atanh(x); 

ParseFloat and ParseInt

Being able to do maths in Javascript is great, but if you remember from our article on types, a number written as a string will not be treated as a number in Javascript. To change a number which is a string, such as «5» to a real number, we can use the function parseFloat (which changes the number to a float), or parseInt , which changes the number to an integer — the difference of course being that an integer has no decimals, while a float does.

Both of these functions accept both numbers, and numbers in mathematical notation.

let myNumber = "12345" // type: String let myOtherNumber = "1.3453"; // type: String  // Let's parse our numbers let parseNumber = parseFloat(myNumber); // Returns 12345 type: Number let parseNumber = parseFloat(myOtherNumber); // Returns 1.3453 type: Number let parseNumber = parseInt(myOtherNumber); // Returns 1 type: Number 

These functions are very useful in vanilla Javascript, where types are not always consistent. Using these, we can take numbers stuck in strings and convert them to real numeric types which we can do calculations with.

Conclusion

Javascript has a lot of interesting ways to do mathematics, and provides many of the common mathematical constants through the Math object. As well as that, we have a number of static functions we can use to manipulate numbers through the same Math function. We’ve learned how to use all of these in this guide, as well as how to coerce a string of numbers into a number with parseInt / parseFloat . All of these techniques are important concepts in Javascript, and really useful when building applications.

More Tips and Tricks for Javascript

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JavaScript Math Object

The JavaScript Math object allows you to perform mathematical tasks on numbers.

Example

The Math Object

Unlike other objects, the Math object has no constructor.

The Math object is static.

All methods and properties can be used without creating a Math object first.

Math Properties (Constants)

The syntax for any Math property is : Math.property .

JavaScript provides 8 mathematical constants that can be accessed as Math properties:

Example

Math.E // returns Euler’s number
Math.PI // returns PI
Math.SQRT2 // returns the square root of 2
Math.SQRT1_2 // returns the square root of 1/2
Math.LN2 // returns the natural logarithm of 2
Math.LN10 // returns the natural logarithm of 10
Math.LOG2E // returns base 2 logarithm of E
Math.LOG10E // returns base 10 logarithm of E

Math Methods

The syntax for Math any methods is : Math.method(number)

Number to Integer

There are 4 common methods to round a number to an integer:

Math.round(x)	Returns x rounded to its nearest integer
Math.ceil(x)	Returns x rounded up to its nearest integer
Math.floor(x)	Returns x rounded down to its nearest integer
Math.trunc(x)	Returns the integer part of x (new in ES6)

Math.round()

Math.round(x) returns the nearest integer:

Examples

Math.ceil()

Math.ceil(x) returns the value of x rounded up to its nearest integer:

Example

Math.floor()

Math.floor(x) returns the value of x rounded down to its nearest integer:

Example

Math.trunc()

Math.trunc(x) returns the integer part of x:

Example

Math.sign()

Math.sign(x) returns if x is negative, null or positive:

Example

Math.trunc() and Math.sign() were added to JavaScript 2015 — ES6.

Math.pow()

Math.pow(x, y) returns the value of x to the power of y:

Example

Math.sqrt()

Math.sqrt(x) returns the square root of x:

Example

Math.abs()

Math.abs(x) returns the absolute (positive) value of x:

Example

Math.sin()

Math.sin(x) returns the sine (a value between -1 and 1) of the angle x (given in radians).

If you want to use degrees instead of radians, you have to convert degrees to radians:

Angle in radians = Angle in degrees x PI / 180.

Example

Math.cos()

Math.cos(x) returns the cosine (a value between -1 and 1) of the angle x (given in radians).

If you want to use degrees instead of radians, you have to convert degrees to radians:

Angle in radians = Angle in degrees x PI / 180.

Example

Math.min() and Math.max()

Math.min() and Math.max() can be used to find the lowest or highest value in a list of arguments:

Example

Example

Math.random()

Math.random() returns a random number between 0 (inclusive), and 1 (exclusive):

Example

You will learn more about Math.random() in the next chapter of this tutorial.

The Math.log() Method

Math.log(x) returns the natural logarithm of x.

The natural logarithm returns the time needed to reach a certain level of growth:

Examples

Math.E and Math.log() are twins.

How many times must we multiply Math.E to get 10?

The Math.log2() Method

Math.log2(x) returns the base 2 logarithm of x.

How many times must we multiply 2 to get 8?

The Math.log10() Method

Math.log10(x) returns the base 10 logarithm of x.

How many times must we multiply 10 to get 1000?

JavaScript Math Methods

Method	Description
abs(x)	Returns the absolute value of x
acos(x)	Returns the arccosine of x, in radians
acosh(x)	Returns the hyperbolic arccosine of x
asin(x)	Returns the arcsine of x, in radians
asinh(x)	Returns the hyperbolic arcsine of x
atan(x)	Returns the arctangent of x as a numeric value between -PI/2 and PI/2 radians
atan2(y, x)	Returns the arctangent of the quotient of its arguments
atanh(x)	Returns the hyperbolic arctangent of x
cbrt(x)	Returns the cubic root of x
ceil(x)	Returns x, rounded upwards to the nearest integer
cos(x)	Returns the cosine of x (x is in radians)
cosh(x)	Returns the hyperbolic cosine of x
exp(x)	Returns the value of E x
floor(x)	Returns x, rounded downwards to the nearest integer
log(x)	Returns the natural logarithm (base E) of x
max(x, y, z, . n)	Returns the number with the highest value
min(x, y, z, . n)	Returns the number with the lowest value
pow(x, y)	Returns the value of x to the power of y
random()	Returns a random number between 0 and 1
round(x)	Rounds x to the nearest integer
sign(x)	Returns if x is negative, null or positive (-1, 0, 1)
sin(x)	Returns the sine of x (x is in radians)
sinh(x)	Returns the hyperbolic sine of x
sqrt(x)	Returns the square root of x
tan(x)	Returns the tangent of an angle
tanh(x)	Returns the hyperbolic tangent of a number
trunc(x)	Returns the integer part of a number (x)

Complete Math Reference

For a complete reference, go to our Complete Math Object Reference.

The reference contains descriptions and examples of all Math properties and methods.

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