The toPrecision()
method returns a string representing the Number
object to the specified precision.
Syntax
numObj.toPrecision([precision])
Parameters
precision
- Optional. An integer specifying the number of significant digits.
Returns
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.
Throws
RangeError
- If
precison
is not between 1 and 100 (inclusive), aRangeError
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.
Examples
Using toPrecision
var 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
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 3rd Edition (ECMA-262) | Standard | Initial definition. Implemented in JavaScript 1.5. |
ECMAScript 5.1 (ECMA-262) The definition of 'Number.prototype.toPrecision' in that specification. |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Number.prototype.toPrecision' in that specification. |
Standard | |
ECMAScript 2017 Draft (ECMA-262) The definition of 'Number.prototype.toPrecision' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |