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toFixed() 方法會使用定點小數表示法(fixed-point notation)來格式化數字。

語法

numObj.toFixed([digits])

參數

digits
Optional. The number of digits to appear after the decimal point; this may be a value between 0 and 20, inclusive, and implementations may optionally support a larger range of values. If this argument is omitted, it is treated as 0.

回傳值

一個代表以定點小數表示法(fixed-point notation)格式化數字後的字串。

例外

RangeError
If digits is too small or too large. Values between 0 and 100, inclusive, will not cause a RangeError. Implementations are allowed to support larger and smaller values as chosen.
TypeError
If this method is invoked on an object that is not a Number.

說明

toFixed() returns a string representation of numObj that does not use exponential notation and has exactly digits digits after the decimal place. The number is rounded if necessary, and the fractional part is padded with zeros if necessary so that it has the specified length. If numObj is greater than 1e+21, this method simply calls Number.prototype.toString() and returns a string in exponential notation.

範例

Using toFixed

var numObj = 12345.6789;

numObj.toFixed();       // Returns '12346': note rounding, no fractional part
numObj.toFixed(1);      // Returns '12345.7': note rounding
numObj.toFixed(6);      // Returns '12345.678900': note added zeros
(1.23e+20).toFixed(2);  // Returns '123000000000000000000.00'
(1.23e-10).toFixed(2);  // Returns '0.00'
2.34.toFixed(1);        // Returns '2.3'
2.35.toFixed(1);        // Returns '2.4'. Note that it rounds up in this case.
-2.34.toFixed(1);       // Returns -2.3 (due to operator precedence, negative number literals don't return a string...)
(-2.34).toFixed(1);     // Returns '-2.3' (...unless you use parentheses)

規範

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.toFixed' in that specification.
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Number.prototype.toFixed' in that specification.
Standard  
ECMAScript Latest Draft (ECMA-262)
The definition of 'Number.prototype.toFixed' in that specification.
Draft  

瀏覽器相容性

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes Yes1 Yes Yes Yes
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes Yes4 Yes Yes Yes

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