JavaScript Number Type

Round

We can round numbers up and down as we want by using the Math.round, Math.ceil and Math.floor static methods or by using the toPrecision method.

• Math.round: Rounds to the closest integer.
• Math.ceil: Rounds up to the closest integer.
• Math.floor: Rounds down to the closest integer.
• toPrecision: Returns a string with the number in the specified precision.

Code example: Math.round

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const a = 12.567
const b = 13.456

console.log(Math.round(a)) // 13
console.log(Math.round(b)) // 13

We can see that a is rounded up because the fractional portion of the number is greater than 0.5.

Code example: Math.ceil

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const a = 12.567
const b = 13.456

console.log(Math.ceil(a)) // 13
console.log(Math.ceil(b)) // 14

ceil always rounds up, so both numbers end up rounded up to the nearest integer.

Code example: Math.floor

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const a = 12.567
const b = 13.456

console.log(Math.floor(a)) // 12
console.log(Math.floor(b)) // 13

floor always rounds down, so both numbers end up rounded down to the nearest integer.

Code example: toPrecision

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const a = 12.567
const b = 13.456

console.log(a.toPrecision(2)) // "13"
console.log(b.toPrecision(2)) // "13"

console.log(a.toPrecision(3)) // "12.6"
console.log(b.toPrecision(3)) // "13.5"

toPrecision with precision set to two significant digits is almost identical to round except that we get a string value back instead.

When we set the precision to three significant digits, our numbers are rounded up to nearest tenth.