Javascript [Electronic resources] : The Definitive Guide (4th Edition) نسخه متنی

Availability

JavaScript 1.5; JScript 5.5, ECMAScript v3

Synopsis

number.toPrecision(precision)

Arguments

precision

The number of significant digits to appear in the returned string.
This may be a value between 1 and 21, inclusive. Implementations are
allowed to optionally support larger and smaller values of
precision. If this argument is omitted,
the toString( ) method is used instead to convert
the number to a base-10 value.

Returns

A string representation of number that
contains precision significant digits. If
precision is large enough to include all
the digits of the integer part of number,
the returned string uses fixed-point notation. Otherwise, exponential
notation is used with one digit before the decimal place and
precision -1 digits after the decimal
place. The number is rounded or padded with zeros as necessary.

Throws

RangeError

If digits is too small or too large.
Values between 1 and 21, inclusive, will not cause a RangeError.
Implementations are allowed to support larger and smaller values as
well.

TypeError

If this method is invoked on an object that is not a Number.

Example

var n = 12345.6789;
n.toPrecision(1);   // Returns 1e+4
n.toPrecision(3);   // Returns 1.23e+4
n.toPrecision(5);   // Returns 12346: note rounding
n.toPrecision(10);  // Returns 12345.67890: note added zero

See Also

Number.toExponential( ), Number.toFixed( ), Number.toLocaleString( ),
Number.toString( )