The toPrecision()
method returns a string representing the Number
object to the specified precision.
numObj.toPrecision([precision])
precision
Optional
A string representing a Number
object in fixed-point or exponential notation rounded to precision
significant digits. See the discussion of rounding in the description of the Number.prototype.toFixed()
method, which also applies to toPrecision()
.
If the precision
argument is omitted, behaves as Number.prototype.toString()
. If the precision
argument is a non-integer value, it is rounded to the nearest integer.
RangeError
precision
is not between 1
and 100
(inclusive), a RangeError
is thrown. Implementations are allowed to support larger and smaller values as well. ECMA-262 only requires a precision of up to 21 significant digits.toPrecision
let numObj = 5.123456 console.log(numObj.toPrecision()) // logs '5.123456' console.log(numObj.toPrecision(5)) // logs '5.1235' console.log(numObj.toPrecision(2)) // logs '5.1' console.log(numObj.toPrecision(1)) // logs '5' numObj = 0.000123 console.log(numObj.toPrecision()) // logs '0.000123' console.log(numObj.toPrecision(5)) // logs '0.00012300' console.log(numObj.toPrecision(2)) // logs '0.00012' console.log(numObj.toPrecision(1)) // logs '0.0001' // note that exponential notation might be returned in some circumstances console.log((1234.5).toPrecision(2)) // logs '1.2e+3'
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Number.prototype.toPrecision' in that specification. |
Desktop | ||||||
---|---|---|---|---|---|---|
toPrecision |
1 | 12 | 1 | 5.5 | 7 | 2 |
Mobile | ||||||
---|---|---|---|---|---|---|
toPrecision |
1 | 18 | 4 | 10.1 | 1 | 1.0 |
Server | |
---|---|
toPrecision |
0.1.100 |
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https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toPrecision