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    Number.prototype.toPrecision()

    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), 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.

    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
    
    // 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. Standard Initial definition. Implemented in JavaScript 1.5.
    ECMAScript 5.1 (ECMA-262)
    The definition of 'Number.prototype.toPrecision' in that specification.
    Standard  
    ECMAScript 6 (ECMA-262)
    The definition of 'Number.prototype.toPrecision' in that specification.
    Release Candidate  

    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)

    See also

    Document Tags and Contributors

    Last updated by: fscholz,