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Math.floor() Method in JS – How to Round Down Numbers

Whenever you invoke Math.floor(), the method rounds down its argument to the nearest integer.

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Syntax of the Math.floor() Method​

Math.floor() accepts only one argument. Here is the syntax:

Math.floor(value);

The value argument represents the number you wish to floor (round down) to the nearest integer.

note
  • Suppose the value argument is already an integer. In that case, Math.floor() will return the same number.
  • Math.floor() is equivalent to -Math.ceil(-value).

Examples​

Below are examples of the Math.floor() method.

How to round down 9 to the nearest integer​

Math.floor(9);

// The invocation above will return: 9

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How to round down 9.999 to the nearest integer​

Math.floor(9.999);

// The invocation above will return: 9

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How to round down -9.999 to the nearest integer​

Math.floor(-9.999);

// The invocation above will return: -10

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The snippet above returned -10 because -10 is the integer directly below -9.999 on the number line. In other words, -9 is greater than -9.999. But -10 is less than -9.999.

How to round down 0.91 to the nearest integer​

Math.floor(0.91);

// The invocation above will return: 0

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Overview​

This article discussed what JavaScript's Math.floor() method does. We also used examples to see how it works.