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Converted to HTML in WebWorks Publisher 2000. manual wdt 1.5"> <META NAME="LASTUPDATED" CONTENT="09/28/00 13:15:36"> <TITLE> Core JavaScript Reference 1.5: </TITLE></HEAD><BODY TEXT="#000000" LINK="#666699" VLINK="#666699" ALINK="#333366" BGCOLOR="#FFFFFF"><MAINCONTENT><NAVIGATIONCONTENT> <TABLE WIDTH="100%" BORDER="0" CELLSPACING="4"> <TR> <TD VALIGN="TOP"> <b><a href="javpkg.html"><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2" COLOR="#993300">Previous</a></FONT> </b><a href="contents.html"><b><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2" COLOR="#993300">Contents</a></FONT></b> <a href="ix.html"><b><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2" COLOR="#993300">Index</a></FONT></b> <a href="netscape.html"><b><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2" COLOR="#993300">Next</a></FONT></b> </TD> </TR> <TR> <TD VALIGN="TOP" ALIGN="RIGHT" BGCOLOR="#CCCCCC"> <FONT FACE="Arial, Helvetica, sans-serif" COLOR="#000000" SIZE="2"><B> Core JavaScript Reference 1.5</B></FONT> </TD> </TR> <TR> </TABLE> <BR></NAVIGATIONCONTENT><BOOKCONTENT> <blockquote><BR><BR> <BR><BR><P><A NAME="1193138"> </A><A NAME="Math"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="5"><B><zrefhead1>Math</zrefhead1></B></FONT><P><A NAME="1193139"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>A built-in object that has properties and methods for mathematical constants and functions. For example, the <FONT FACE="courier, couriernew, monospaced size">Math</FONT> object's <A HREF="math.html#1193490" >PI</A> property has the value of pi.<BR><P><TABLE WIDTH="90%" BORDER="1" CELLPADDING="5" CELLSPACING="0"> <CAPTION></CAPTION><P><FONT FACE=""><B></B></FONT><BR><BR> <TR> <TD VALIGN=TOP COLSPAN=2 ROWSPAN=1><P><A NAME="1193145"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext><I>Core object</I></ztabletext></FONT></TD> </TR> <TR> <TD VALIGN=TOP><P><A NAME="1193149"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext><I>Implemented in</I></ztabletext></FONT> </TD> <TD VALIGN=TOP><P><A NAME="1193151"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>JavaScript 1.0, NES 2.0</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><P><A NAME="1201615"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext><I>ECMA version</I></ztabletext></FONT> </TD> <TD VALIGN=TOP><P><A NAME="1201617"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>ECMA-262</ztabletext></FONT> </TD> </TR></TABLE><P></zparagraph></FONT><P><BR><A NAME="1193152"> </A><A NAME="Created by"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Created by</zrefheader></B></FONT><BR><A NAME="1193156"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The <A HREF="math.html#1193138" >Math</A> object is a top-level, predefined JavaScript object. You can automatically access it without using a constructor or calling a method.</zparagraph></FONT><P><BR><A NAME="1193157"> </A><A NAME="Description"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Description</zrefheader></B></FONT><BR><A NAME="1193158"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>All properties and methods of <FONT FACE="courier, couriernew, monospaced size">Math</FONT> are static. You refer to the constant PI as <FONT FACE="courier, couriernew, monospaced size">Math.PI</FONT> and you call the sine function as <FONT FACE="courier, couriernew, monospaced size">Math.sin(x)</FONT>, where <FONT FACE="courier, couriernew, monospaced size">x</FONT> is the method's argument. Constants are defined with the full precision of real numbers in JavaScript. </zparagraph></FONT><P><A NAME="1193162"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>It is often convenient to use the <A HREF="stmt.html#1004910" >with</A> statement when a section of code uses several <FONT FACE="courier, couriernew, monospaced size">Math</FONT> constants and methods, so you don't have to type "Math" repeatedly. For example,</zparagraph></FONT><P><A NAME="1193163"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>with (Math) {<br> a = PI * r*r<br> y = r*sin(theta)<br> x = r*cos(theta)<br>}</zcodeline></FONT><P><BR><A NAME="1193164"> </A><A NAME="Property Summary"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Property Summary</zrefheader></B></FONT><BR><A NAME="1193226"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><BR><P><TABLE WIDTH="90%" BORDER="1" CELLPADDING="5" CELLSPACING="0"> <CAPTION></CAPTION><P><FONT FACE=""><B></B></FONT><BR><BR> <TR BGCOLOR="#CCCCCC" ALIGN=LEFT VALIGN=TOP> <TH VALIGN=TOP ALIGN=LEFT><A NAME="1193167"> </A><P ALIGN="LEFT"><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><ztablehead>Property</ztablehead></B></FONT></TH> <TH VALIGN=TOP ALIGN=LEFT><A NAME="1193169"> </A><P ALIGN="LEFT"><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><ztablehead>Description</ztablehead></B></FONT></TH> </DIV></TR> <TR> <TD VALIGN=TOP><A NAME="1193174"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1193363" >E</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193176"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Euler's constant and the base of natural logarithms, approximately 2.718.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1216179"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1216604" >LN2</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1216181"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Natural logarithm of 2, approximately 0.693.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193181"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1193389" >LN10</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193183"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Natural logarithm of 10, approximately 2.302.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1216068"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1193465" >LOG2E</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1216070"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Base 2 logarithm of E (approximately 1.442).</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193195"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1217093" >LOG10E</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193197"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Base 10 logarithm of E (approximately 0.434).</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193209"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1193490" >PI</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193211"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Ratio of the circumference of a circle to its diameter, approximately 3.14159.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193216"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1193515" >SQRT1_2</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193218"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Square root of 1/2; equivalently, 1 over the square root of 2, approximately 0.707.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193223"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1193540" >SQRT2</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193225"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Square root of 2, approximately 1.414.</ztabletext></FONT> </TD> </TR></TABLE><P></zparagraph></FONT><P><BR><A NAME="1193227"> </A><A NAME="Method Summary"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Method Summary</zrefheader></B></FONT><BR><A NAME="1193359"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><BR><P><TABLE WIDTH="90%" BORDER="1" CELLPADDING="5" CELLSPACING="0"> <CAPTION></CAPTION><P><FONT FACE=""><B></B></FONT><BR><BR> <TR BGCOLOR="#CCCCCC" ALIGN=LEFT VALIGN=TOP> <TH VALIGN=TOP ALIGN=LEFT><A NAME="1193230"> </A><P ALIGN="LEFT"><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><ztablehead>Method</ztablehead></B></FONT></TH> <TH VALIGN=TOP ALIGN=LEFT><A NAME="1193232"> </A><P ALIGN="LEFT"><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><ztablehead>Description</ztablehead></B></FONT></TH> </DIV></TR> <TR> <TD VALIGN=TOP><A NAME="1193237"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1195395" >abs</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193239"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Returns the absolute value of a number.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193244"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1195429" >acos</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193246"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Returns the arccosine (in radians) of a number.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193251"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1195485" >asin</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193253"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Returns the arcsine (in radians) of a number.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193258"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1195541" >atan</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193260"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Returns the arctangent (in radians) of a number.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193265"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1195597" >atan2</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193267"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Returns the arctangent of the quotient of its arguments. </ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193272"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1195654" >ceil</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193274"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Returns the smallest integer greater than or equal to a number.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193279"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1195695" >cos</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193281"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Returns the cosine of a number.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193286"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1196408" >exp</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193288"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Returns E<SUP>number</SUP>, where <FONT FACE="courier, couriernew, monospaced size">number</FONT> is the argument, and E is Euler's constant, the base of the natural logarithms.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193293"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1196455" >floor</A></zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1193295"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Returns the largest integer less than or equal to a number.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1193300"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline><A HREF="math.html#1196917" >log</A>⌨️ 快捷键说明
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