Math in JavaScript

As we delve into JavaScript further it is important to understand how to perform mathematical operations. In JavaScript there is an object called Math that will help us out. This includes properties and methods useful in modifying numbers and providing data to your audience. Below I will present some of these in an effort to provide an introduction to doing math in JavaScript. Keep in mind math is an incredibly vast topic, and the Math object itself contains a plethora of mathematical operations encompassing a large area within the field. I will focus this lesson on the basics to get you started. If you find yourself still curious we always encourage further research. We are just your kickstarter.


Math Methods

Math.random() provides a random number between 0 and 1, including 0 but not 1.

// your results will vary
Math.random(); // 0.2898583256173879  
Math.random(); // 0.17178424587473273  

Math.ceil(number) and Math.floor(number) are used to round numbers. Math.ceil rounds numbers UP to the closest integer, where Math.floor rounds numbers DOWN.

Math.ceil(.04);  // 1  
Math.ceil(55.12); // 56  
Math.ceil(66.86); // 67

Math.floor(.99); // 0  
Math.floor(112.12); // 112  
Math.floor(88.88); // 88  

Let's incorporate Math.floor() and Math.random() to produce a random integer between 1 & 100.

// results will vary
Math.floor(Math.random() * 100) + 1; // 38  
// Math.random() * 100 => produces a number between 0 & 99.9999.
// Then we round it down, so we are limited to 0 and 99.
// the + 1 allows us the possibility to reach 100, accounting for the rounding down

// written as a function
function getRandomNumber(lowVal, highVal){  
  return Math.floor(Math.random() * highVal) + lowVal;
}
getRandomNumber(1, 100);  

Math.round() is used to round numbers to the nearest whole number.

Math.round(5.75); // 6  
// round a price of a product after accounting for sales tax
const CA_TAX = 0.0925;  
function rounder(price){  
  var price = price * (1 + CA_TAX);
  return Math.round(price);
}
rounder(25.43);  
// returns 28 = number after taxes rounded to the nearest whole number

In this example we created a rounder function to round our product to the nearest whole number, after we accounted for tax.

Math.min(x1, x2, ..., xi) and Math.max(x1, x2, ..., xi) return the lowest number in a set of numbers. If no arguments are given the result is infinity, and if an input is not valid, the result is NaN.

var x = -12;  
var y = 23;  
z = Math.min(x, y); // -12  
// z is assigned to the lowest value in the set (x,y) in this case -12.
Math.max(x, y); // 23  

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

// 10^2 or 10 * 10
Math.pow(10, 2); // 100  
// 4^8
Math.pow(4, 8); // 65536  

Math.sqrt(number) returns the square root of a number.

Math.sqrt(16); // 16  
Math.sqrt(99); // 9.9498743710662  

Along with these methods, there are also a variety of properties to represent certain mathematical constants, that may be great references for some of your calculations.


Math Properties

Math.PI: Returns the value of PI.

Math.SQRT_2: Returns the square root of 2.

Math.SQRT1_2: Returns the square root of 1/2, which is equivalent to 1 over the square root of 2.

Math.E: Returns Euler's constant and the base of natural logarithms.

Math.LN2: Returns the natural logarithm of 2.

Math.LN10: Returns the natural logarithm of 10.

Math.LOG2E: Returns the base 2 logarithm of E.

Math.LOG10E: Returns the base 10 logarithm of E.

Math.PI        // 3.141592653589793  
Math.SQRT2     // 1.4142135623730951  
Math.SQRT1_2   // 0.7071067811865476  
Math.E         // 2.718281828459045  
Math.LN2       // 0.6931471805599453  
Math.LN10      // 2.302585092994046  
Math.LOG2E     // 1.4426950408889634  
Math.LOG10E    // 0.4342944819032518  

Feel free to delve into these methods and properties available to us via the Math object, as math is an incredibly useful thing in JavaScript, and programming in general. Knowledge of how to perform mathematical operations in programming will make life easier when presenting numbers. For more information and a list of all the methods and properties associated with Math, checkout Mozilla Developers Network.


Further Reading:

Michael Montero

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