Javascript: Rounding a real number(round,toFixed,parseFloat)

Math.round method rounds a real number to nearest integer.

Consider following code snippet.

Code:

let number = 34.5678

console.log(Math.round(number))

Output:

35

Explanation:

The value of number variable is rounded to the nearest integer.

How to round a real number to certain decimal places ?

In JavaScript, you can use the toFixed() method to round

a real number to a certain number of decimal places.

Code:

let num = 12.34444;

let roundedNum = num.toFixed(2);

console.log(roundedNum);

console.log(typeof roundedNum);

roundedNum = parseFloat(roundedNum);

console.log(typeof roundedNum);

Output:

12.34

string

number

Another Example:

Code:

let num = 12.34567;

let roundedNum = num.toFixed(2);

console.log(roundedNum);

console.log(typeof roundedNum);

roundedNum = parseFloat(roundedNum);

console.log(typeof roundedNum);

Output:

12.35

string

The toFixed() method converts a number into a string,

representing the number rounded to a specified number of decimal places.

parseFloat convert string to number.

parseFloat in detail:

parseFloat() is a built-in JavaScript function that parses a string

argument and returns a floating-point number. It attempts to convert

the string into a number, considering only the characters that make up

a valid number (digits, a decimal point, and an optional positive or

negative sign at the beginning).Any non-numeric characters or spaces

after the number are ignored.

Code:

let numStr3 = "ABC123";

let num3 = parseFloat(numStr3);

console.log(num3);

Output:

NaN

Explanation:since the string doesn't represent a valid number we get NaN.

Another example:

Code:

let numStr4 = " 30.75 ";

let num4 = parseFloat(numStr4);

console.log(num4);

Output:

30,75

Note:leading and trailing spaces are ignored

Another Example:

Code:

let numStr4 = "12.567$30.75#";

let num4 = parseFloat(numStr4);

console.log(num4);

Output:

12.567