Learning JavaScript Math.round() method

Posted on Dec 30, 2020

Let's learn how JavaScript Math.round() method works

The JavaScript Math.round() method is used to round a number with decimal values to the nearest whole number (also called an integer)

If the decimal value is .5 or higher, the method will return the higher integer:

Math.round(6.5);

// returns 7

When the decimal value is lower than .5 the method will return the lower integer:

Math.round(6.4);

// returns 6

The method only accepts one number, so if you pass multiple numbers, it will only return the first number and ignore the rest:

Math.round(4.5, 7, 8);

// returns 5

If you pass a string, an object, or an array to the method, it will return NaN which stands for Not a Number:

Math.round("Hello there!");
Math.round([1, 2, 3]);
Math.round({ name: "Andy" });

// returns NaN

When you pass a boolean value of true or false it will return 1 for true and 0 for false:

Math.round(true);
// returns 1

Math.round(false);
// returns 0

Other rounding methods

If you want to always round a number up, use [the Math.ceil() method]( {{ <ref “/18-javascript-math-ceil”> }} ).

If you want to always round a number down, use the Math.floor() method.

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