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</B></FONT><BR><A NAME="1014324"> </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> <TD VALIGN=TOP><A NAME="1014321"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>label</zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1014323"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Identifier associated with the label of the statement. </ztabletext></FONT> </TD> </TR></TABLE><P></zparagraph></FONT><P><BR><A NAME="1010036"> </A><A NAME="Description"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Description</zrefheader></B></FONT><BR><A NAME="1031807"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The <FONT FACE="courier, couriernew, monospaced size">break</FONT> statement includes an optional label that allows the program to break out of a labeled statement. The statements in a labeled statement can be of any type.</zparagraph></FONT><P><BR><A NAME="1031799"> </A><A NAME="Examples"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Examples</zrefheader></B></FONT><BR><A NAME="1010037"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The following function has a <FONT FACE="courier, couriernew, monospaced size">break</FONT> statement that terminates the <A HREF="stmt.html#1004896" >while</A> loop when <FONT FACE="courier, couriernew, monospaced size">e</FONT> is 3, and then returns the value 3 * <FONT FACE="courier, couriernew, monospaced size">x</FONT>.</zparagraph></FONT><P><A NAME="1004786"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>function testBreak(x) {<br> var i = 0;<br> while (i < 6) {<br> if (i == 3)<br> break;<br> i++;<br> }<br> return i*x;<br>}</zcodeline></FONT><P><BR><A NAME="1014796"> </A><A NAME="See also"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>See also</zrefheader></B></FONT><BR><A NAME="1014820"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><A HREF="stmt.html#1078923" >continue</A>, <A HREF="stmt.html#1018088" >label</A>, <A HREF="stmt.html#1018610" >switch</A></zparagraph></FONT><P><BR><BR><A NAME="1077887"> </A><A NAME="const"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="4"><zhead1>const</zhead1><HR SIZE="2" NOSHADE></FONT><BR><A NAME="1077897"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Declares a readonly, named constant. <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><P><A NAME="1077890"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext><I>Implemented in</I></ztabletext></FONT> </TD> <TD VALIGN=TOP><P><A NAME="1077892"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>JavaScript 1.5, NES 6.0 (Netscape extension, C engine only), </ztabletext></FONT> </TD> </TR></TABLE><P></zparagraph></FONT><P><BR><A NAME="1078082"> </A><A NAME="Syntax"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Syntax</zrefheader></B></FONT><BR><A NAME="1078083"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>const <I>constname</I> [= <I>value</I>] [..., <I>constname</I> [= <I>value</I>] ]</zcodeline></FONT><P><BR><A NAME="1078084"> </A><A NAME="Parameters"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Parameters</zrefheader></B></FONT><BR><A NAME="1077910"> </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> <TD VALIGN=TOP><A NAME="1077903"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>varname</zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1077905"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Constant name. It can be any legal identifier.</ztabletext></FONT> </TD> </TR> <TR> <TD VALIGN=TOP><A NAME="1077907"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>value</zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1077909"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Value of the constant and can be any legal expression.</ztabletext></FONT> </TD> </TR></TABLE><P></zparagraph></FONT><P><BR><A NAME="1077911"> </A><A NAME="Description"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Description</zrefheader></B></FONT><BR><A NAME="1078332"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Creates a constant that can be global or local to the function in which it is declared. Constants follow the same scope rules as variables. </zparagraph></FONT><P><A NAME="1080040"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The value of a constant cannot change through re-assignment, and a constant cannot be re-declared.</zparagraph></FONT><P><A NAME="1078333"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>A constant cannot share the same name as a function or variable in the same scope.</zparagraph></FONT><P><BR><A NAME="1078336"> </A><A NAME="Examples"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Examples</zrefheader></B></FONT><BR><A NAME="1078620"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The script:</zparagraph></FONT><P><A NAME="1078920"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>const a = 7;</zcodeline></FONT><P><A NAME="1079008"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>document.writeln("a is " + a + ".");</zcodeline></FONT><P><A NAME="1081885"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>produces the output:</zparagraph></FONT><P><A NAME="1079005"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>a is 7. </zcodeline></FONT><P><BR><BR><A NAME="1078923"> </A><A NAME="continue"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="4"><zhead1>continue</zhead1><HR SIZE="2" NOSHADE></FONT><BR><A NAME="1073873"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Restarts a <FONT FACE="courier, couriernew, monospaced size">while</FONT>, <FONT FACE="courier, couriernew, monospaced size">do-while</FONT>, <FONT FACE="courier, couriernew, monospaced size">for</FONT>, or <FONT FACE="courier, couriernew, monospaced size">label</FONT> statement.<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><P><A NAME="1032602"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext><I>Implemented in</I></ztabletext></FONT> </TD> <TD VALIGN=TOP><P><A NAME="1041739"> </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="1050120"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext><I>ECMA version</I></ztabletext></FONT> </TD> <TD VALIGN=TOP><P><A NAME="1050122"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>ECMA-262 (for the unlabeled version)<br>ECMA-262, Edition 3 (for the labeled version)</ztabletext></FONT> </TD> </TR></TABLE><P></zparagraph></FONT><P><BR><A NAME="1032605"> </A><A NAME="Syntax"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Syntax</zrefheader></B></FONT><BR><A NAME="1032606"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>continue [<I>label</I>]</zcodeline></FONT><P><BR><A NAME="1015179"> </A><A NAME="Parameter"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Parameter</zrefheader></B></FONT><BR><A NAME="1015226"> </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> <TD VALIGN=TOP><A NAME="1015306"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>label</zcodeline></FONT><P> </TD> <TD VALIGN=TOP><P><A NAME="1015325"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><ztabletext>Identifier associated with the label of the statement.</ztabletext></FONT> </TD> </TR></TABLE><P></zparagraph></FONT><P><BR><A NAME="1004801"> </A><A NAME="Description"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Description</zrefheader></B></FONT><BR><A NAME="1032853"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>In contrast to the <A HREF="stmt.html#1081298" >break</A> statement, <FONT FACE="courier, couriernew, monospaced size">continue</FONT> does not terminate the execution of the loop entirely: instead,</zparagraph></FONT><P><ul><A NAME="1032854"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B> <li></B><zsmartlist1>In a <A HREF="stmt.html#1004896" >while</A> loop, it jumps back to the <FONT FACE="courier, couriernew, monospaced size">condition</FONT>.</zsmartlist1></FONT><P><A NAME="1032855"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B> <li></B><zsmartlist1>In a <A HREF="stmt.html#1004804" >for</A> loop, it jumps to the <FONT FACE="courier, couriernew, monospaced size">update</FONT> expression.</zsmartlist1></FONT><P></ul><A NAME="1032856"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The <FONT FACE="courier, couriernew, monospaced size">continue</FONT> statement can now include an optional label that allows the program to terminate execution of a labeled statement and continue to the specified labeled statement. This type of continue must be in a looping statement identified by the label used by <FONT FACE="courier, couriernew, monospaced size">continue</FONT>.</zparagraph></FONT><P><BR><A NAME="1032840"> </A><A NAME="Examples"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><B><zrefheader>Examples</zrefheader></B></FONT><BR><A NAME="1004802"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><B>Example 1.</B> The following example shows a <FONT FACE="courier, couriernew, monospaced size">while</FONT> loop that has a <A HREF="stmt.html#1078923" >continue</A> statement that executes when the value of <FONT FACE="courier, couriernew, monospaced size">i</FONT> is 3. Thus, <FONT FACE="courier, couriernew, monospaced size">n</FONT> takes on the values 1, 3, 7, and 12.</zparagraph></FONT><P><A NAME="1004803"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>i = 0;<br>n = 0;<br>while (i < 5) {<br> i++;<br> if (i == 3)<br> continue;<br> n += i;<br>}</zcodeline></FONT><P><A NAME="1015392"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><B>Example 2.</B> In the following example, a statement labeled <FONT FACE="courier, couriernew, monospaced size">checkiandj</FONT> contains a statement labeled <FONT FACE="courier, couriernew, monospaced size">checkj</FONT>. If <FONT FACE="courier, couriernew, monospaced size">continue</FONT> is encountered, the program continues at the top of the <FONT FACE="courier, couriernew, monospaced size">checkj</FONT> statement. Each time <FONT FACE="courier, couriernew, monospaced size">continue</FONT> is encountered, <FONT FACE="courier, couriernew, monospaced size">checkj</FONT> reiterates until its condition returns false. When false is returned, the remainder of the <FONT FACE="courier, couriernew, monospaced size">checkiandj</FONT> statement is completed. <FONT FACE="courier, couriernew, monospaced size">checkiandj</FONT> reiterates until its condition returns false. When false is returned, the program continues at the statement following <FONT FACE="courier, couriernew, monospaced size">checkiandj</FONT>.</zparagraph></FONT><P><A NAME="1015846"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>If <FONT FACE="courier, couriernew, monospaced size">continue</FONT> had a label of <FONT FACE="courier, couriernew, monospaced size">checkiandj</FONT>, the program would continue at the top of the <FONT FACE="courier, couriernew, monospaced size">checkiandj</FONT> statement.</zparagraph></FONT><P><A NAME="1026373"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline>checkiandj : <br>while (i<4) {<br> document.write(i + "<BR>"); <br> i+=1;</zcodeline></FONT><P><A NAME="1027440"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2"><zcodeline> checkj : <br> while (j>4) {<br> document.write(j + "<BR>"); <br> j-=1; <br> if ((j%2)==0)<br> continue checkj; <br> document.write(j + " is odd.<BR>");<br> } <br> document.write("i = " + i + "<br>");<br> document.write("j = " + j + "<br>"); <br>}</zcodeline></FONT><P><BR><A NAME="1015924"> </A>?? 快捷鍵說(shuō)明
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