number.html

javascript 1.5规范

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<A NAME="1193220"> </A>
<A NAME="Method Summary"> </A>
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<zrefheader>Method Summary</zrefheader>
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<A NAME="1193240"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><BR>
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<ztablehead>Method</ztablehead>
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<ztablehead>Description</ztablehead>
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    <TD VALIGN=TOP><A NAME="1200949"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>toExponential
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<A NAME="1200951"> </A>
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<ztabletext>Returns a string representing the number in exponential notation.</ztabletext>
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<zcodeline><A HREF="number.html#1200964"  >toFixed</A>
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<A NAME="1199938"> </A>
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<ztabletext>Returns a string representing the number in fixed-point notation.</ztabletext>
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    <TD VALIGN=TOP><A NAME="1201374"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>toPrecision
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<A NAME="1201376"> </A>
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<ztabletext>Returns a string representing the number to a specified precision in fixed-point notation.</ztabletext>
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    <TD VALIGN=TOP><A NAME="1199947"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline><A HREF="number.html#1201831"  >toSource</A>
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<A NAME="1199949"> </A>
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<ztabletext>Returns an object literal representing the specified Number object; you can use this value to create a new object. Overrides the <A HREF="object.html#1193320"  >Object.toSource</A> method.</ztabletext>
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    <TD VALIGN=TOP><A NAME="1199957"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline><A HREF="number.html#1193464"  >toString</A>
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<A NAME="1199959"> </A>
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<ztabletext>Returns a string representing the specified object. Overrides the <A HREF="object.html#1193350"  >Object.toString</A> method.</ztabletext>
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    <TD VALIGN=TOP><A NAME="1199967"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline><A HREF="number.html#1195199"  >valueOf</A>
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<A NAME="1199969"> </A>
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<ztabletext>Returns the primitive value of the specified object. Overrides the <A HREF="object.html#1193540"  >Object.valueOf</A> method.</ztabletext>
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<A NAME="1196162"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>In addition, this object inherits the <A HREF="object.html#1193628"  >watch</A> and <A HREF="object.html#1193499"  >unwatch</A> methods from <A HREF="object.html#1193136"  >Object</A>.</zparagraph>
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<A NAME="1193241"> </A>
<A NAME="Examples"> </A>
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<zrefheader>Examples</zrefheader>
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<A NAME="1193242"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><B>Example 1.</B> The following example uses the <FONT FACE="courier, couriernew, monospaced size">Number</FONT> object's properties to assign values to several numeric variables:</zparagraph>
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<A NAME="1193243"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>biggestNum = Number.MAX_VALUE;<br>
smallestNum = Number.MIN_VALUE;<br>
infiniteNum = Number.POSITIVE_INFINITY;<br>
negInfiniteNum = Number.NEGATIVE_INFINITY;<br>
notANum = Number.NaN;
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<A NAME="1193244"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><B>Example 2.</B> The following example creates a <FONT FACE="courier, couriernew, monospaced size">Number</FONT> object, <FONT FACE="courier, couriernew, monospaced size">myNum</FONT>, then adds a <FONT FACE="courier, couriernew, monospaced size">description</FONT> property to all <FONT FACE="courier, couriernew, monospaced size">Number</FONT> objects. Then a value is assigned to the <FONT FACE="courier, couriernew, monospaced size">myNum</FONT> object's <FONT FACE="courier, couriernew, monospaced size">description</FONT> property.</zparagraph>
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<A NAME="1193245"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>myNum = new Number(65);<br>
Number.prototype.description=null;<br>
myNum.description="wind speed";
</zcodeline>
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<A NAME="1196194"> </A>
<A NAME="constructor"> </A>
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<zrefhead2>constructor</zrefhead2>
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<A NAME="1196195"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Specifies the function that creates an object's prototype. Note that the value of this property is a reference to the function itself, not a string containing the function's name.<BR>
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<A NAME="1196198"> </A>
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<ztabletext><I>Property of</I></ztabletext>
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<A NAME="1196203"> </A>
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<ztabletext><A HREF="number.html#1193137"  >Number</A></ztabletext>
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<A NAME="1196205"> </A>
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<ztabletext><I>Implemented in</I></ztabletext>
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<A NAME="1196207"> </A>
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<ztabletext>JavaScript 1.1, NES 2.0</ztabletext>
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<A NAME="1196209"> </A>
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<ztabletext><I>ECMA version</I></ztabletext>
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<A NAME="1196211"> </A>
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<ztabletext>ECMA-262</ztabletext>
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<A NAME="1196212"> </A>
<A NAME="Description"> </A>
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<zrefheader>Description</zrefheader>
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<A NAME="1196216"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>See <A HREF="object.html#1193229"  >Object.constructor</A>.</zparagraph>
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<A NAME="1193249"> </A>
<A NAME="MAX_VALUE"> </A>
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<zrefhead2>MAX_VALUE</zrefhead2>
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<A NAME="1193266"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The maximum numeric value representable in JavaScript.<BR>
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<A NAME="1193252"> </A>
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<ztabletext><I>Property of</I></ztabletext>
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<A NAME="1193257"> </A>
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<ztabletext><A HREF="number.html#1193137"  >Number</A></ztabletext>
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<A NAME="1193259"> </A>
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<ztabletext><I>Static, Read-only</I></ztabletext>
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<A NAME="1193263"> </A>
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<ztabletext><I>Implemented in</I></ztabletext>
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<A NAME="1193265"> </A>
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<ztabletext>JavaScript 1.1, NES 2.0</ztabletext>
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<A NAME="1194452"> </A>
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<ztabletext><I>ECMA version</I></ztabletext>
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<A NAME="1194454"> </A>
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<ztabletext>ECMA-262</ztabletext>
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<A NAME="1193267"> </A>
<A NAME="Description"> </A>
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<zrefheader>Description</zrefheader>
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<A NAME="1193268"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The <FONT FACE="courier, couriernew, monospaced size">MAX_VALUE</FONT> property has a value of approximately 1.79E+308. Values larger than <FONT FACE="courier, couriernew, monospaced size">MAX_VALUE</FONT> are represented as <FONT FACE="courier, couriernew, monospaced size">"Infinity"</FONT>.</zparagraph>
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<A NAME="1193269"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Because <FONT FACE="courier, couriernew, monospaced size">MAX_VALUE</FONT> is a static property of <FONT FACE="courier, couriernew, monospaced size">Number</FONT>, you always use it as <FONT FACE="courier, couriernew, monospaced size">Number.MAX_VALUE</FONT>, rather than as a property of a <FONT FACE="courier, couriernew, monospaced size">Number</FONT> object you created.</zparagraph>
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<A NAME="1193270"> </A>
<A NAME="Examples"> </A>
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<zrefheader>Examples</zrefheader>
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<A NAME="1193271"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The following code multiplies two numeric values. If the result is less than or equal to <FONT FACE="courier, couriernew, monospaced size">MAX_VALUE</FONT>, the <FONT FACE="courier, couriernew, monospaced size">func1</FONT> function is called; otherwise, the <FONT FACE="courier, couriernew, monospaced size">func2</FONT> function is called.</zparagraph>
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<A NAME="1193272"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>if (num1 * num2 &lt;= Number.MAX_VALUE)<br>
&nbsp;&nbsp;&nbsp;func1()<br>
else<br>
&nbsp;&nbsp;&nbsp;func2()
</zcodeline>
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<A NAME="1193275"> </A>
<A NAME="MIN_VALUE"> </A>
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<zrefhead2>MIN_VALUE</zrefhead2>
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<A NAME="1193292"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The smallest positive numeric value representable in JavaScript.<BR>
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<A NAME="1193278"> </A>
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<ztabletext><I>Property of</I></ztabletext>
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<A NAME="1193283"> </A>
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<ztabletext><A HREF="number.html#1193137"  >Number</A></ztabletext>
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