JavaScript Numbers
This Scrimba screencast was created by Dylan C. Israel.
JavaScript has only one type of number. Numbers can be written as whole numbers, as known as integers, or decimal numbers, as known as floating-point numbers.
TIP
When assigning a number to a variable, no quotes or backticks should be used.
const wholeNumber = 7
const decimal = 7.77
Methods and Functions
JavaScript includes useful methods and functions for working with numbers. These methods will work with any type of numbers with (literals, variables, or expressions).
The toFixed() Method
The toFixed() method returns a string, with the number written with a specified number of decimals.
NOTE
If the original number contains more decimals than specified, then the additional numbers will be rounded. If the original number contains fewer decimals than specified, then zeros will be added to the end.
const pi = 3.1415
console.log(pi.toFixed(0)) // 3
console.log(pi.toFixed(1)) // 3.1
console.log(pi.toFixed(3)) // 3.142
console.log(pi.toFixed(5)) // 3.14150
The toPrecision() Method
The toPrecision() method returns a string with a number written with a specified length.
NOTE
If the original number contains more digits than specified, then the additional numbers will be rounded. If the original number contains fewer digits than specified, then zeros will be added to the end.
const a = 3.1415
console.log(a.toPrecision(1)) // 3
console.log(a.toPrecision(3)) // 3.14
console.log(a.toPrecision(5)) // 3.1415
console.log(a.toPrecision(7)) // 3.141500
The parseInt() Function
The parseInt() function returns an integer (whole number) from the value provided. The value provide can be a number, string, or array.
NOTE
The parseInt() function will return null if the first value encountered cannot be converted to a number.
console.log(parseInt(3.1415)) // 3
console.log(parseInt('3.1415')) // 3
console.log(parseInt([3.1415])) // 3
console.log(parseInt('pi = 3.1415')) // null
The parseFloat() Function
The parseFloat() function returns an floating point number (decimal) from the value provided. The value provide can be a number, string, or array.
NOTE
The parseFloat() function will return null if the first value encountered cannot be converted to a number.
console.log(parseFloat(3.1415)) // 3.1415
console.log(parseFloat('3.1415')) // 3.1415
console.log(parseFloat([3.1415])) // 3.1415
console.log(parseFloat('pi = 3.1415')) // null