object.html

javascript 1.5规范

&nbsp;&nbsp;&nbsp;this.name=name<br>
&nbsp;&nbsp;&nbsp;this.breed=breed<br>
&nbsp;&nbsp;&nbsp;this.color=color<br>
&nbsp;&nbsp;&nbsp;this.sex=sex<br>
}<br>
theDog = new Dog("Gabby","Lab","chocolate","girl")
</zcodeline>
</FONT>
<P>
<A NAME="1204667"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Calling the <FONT FACE="courier, couriernew, monospaced size">toSource</FONT> method of <FONT FACE="courier, couriernew, monospaced size">theDog</FONT> displays the JavaScript source that defines the object:</zparagraph>
</FONT>
<P>
<A NAME="1204789"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>theDog.toSource()<br>
//returns "{name:"Gabby", breed:"Lab", color:"chocolate", sex:"girl"}
</zcodeline>
</FONT>
<P><BR>
<A NAME="1193343"> </A>
<A NAME="See also"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zrefheader>See also</zrefheader>
</B>
</FONT>
<BR>

<A NAME="1193347"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><A HREF="object.html#1193350"  >Object.toString</A></zparagraph>
</FONT>
<P>
<BR>
<P>
<A NAME="1193350"> </A>
<A NAME="toString"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="4">
<B>
<zrefhead2>toString</zrefhead2>
</B>
</FONT>
<P>

<A NAME="1193363"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Returns a string representing the specified object.<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="1193353"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext><I>Method of</I></ztabletext>
</FONT>&nbsp;</TD>
    <TD VALIGN=TOP>
<P>
<A NAME="1193358"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext><A HREF="object.html#1193136"  >Object</A></ztabletext>
</FONT>&nbsp;</TD>
  </TR>
  <TR>
    <TD VALIGN=TOP>
<P>
<A NAME="1193360"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext><I>Implemented in</I></ztabletext>
</FONT>&nbsp;</TD>
    <TD VALIGN=TOP>
<P>
<A NAME="1193362"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext>JavaScript 1.0</ztabletext>
</FONT>&nbsp;</TD>
  </TR>
  <TR>
    <TD VALIGN=TOP>
<P>
<A NAME="1196496"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext><I>ECMA version</I></ztabletext>
</FONT>&nbsp;</TD>
    <TD VALIGN=TOP>
<P>
<A NAME="1196498"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext>ECMA-262</ztabletext>
</FONT>&nbsp;</TD>
  </TR>
</TABLE>



<P></zparagraph>
</FONT>
<P>
<BR>
<A NAME="1203456"> </A>
<A NAME="Syntax"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zrefheader>Syntax</zrefheader>
</B>
</FONT>
<BR>
<A NAME="1203457"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>toString()
</zcodeline>
</FONT>
<P><BR>
<A NAME="1193421"> </A>
<A NAME="Description"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zrefheader>Description</zrefheader>
</B>
</FONT>
<BR>

<A NAME="1193422"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Every object has a <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method that is automatically called when it is to be represented as a text value or when an object is referred to in a string concatenation. For example, the following examples require <FONT FACE="courier, couriernew, monospaced size">theDog</FONT> to be represented as a string:</zparagraph>
</FONT>
<P>
<A NAME="1193423"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>document.write(theDog)<br>
document.write("The dog is " + theDog)
</zcodeline>
</FONT>
<P>
<A NAME="1200394"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>By default, the <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method is inherited by every object descended from <FONT FACE="courier, couriernew, monospaced size">Object</FONT>. You can override this method for custom objects that you create. If you do not override <FONT FACE="courier, couriernew, monospaced size">toString</FONT> in a custom object, <FONT FACE="courier, couriernew, monospaced size">toString</FONT> returns <FONT FACE="courier, couriernew, monospaced size">[object </FONT><FONT FACE="courier, couriernew, monospaced size"><I>type</I></font><FONT FACE="courier, couriernew, monospaced size">]</FONT>, where <FONT FACE="courier, couriernew, monospaced size"><I>type</I></font> is the object type or the name of the constructor function that created the object.</zparagraph>
</FONT>
<P>

<A NAME="1203849"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>For example:</zparagraph>
</FONT>
<P>
<A NAME="1203854"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>var o = new Object()<br>
o.toString // returns [object Object]
</zcodeline>
</FONT>
<P><P>
<A NAME="1193426"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zheadrunin>Built-in toString methods. </zheadrunin>
</B>
</FONT>

<A NAME="1203699"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Every built-in core JavaScript object overrides the <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method of <FONT FACE="courier, couriernew, monospaced size">Object</FONT> to return an appropriate value. JavaScript calls this method whenever it needs to convert an object to a string.</zparagraph>
</FONT>
<P>
<P>
<A NAME="1193453"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zheadrunin>Overriding the default toString method. </zheadrunin>
</B>
</FONT>

<A NAME="1193454"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>You can create a function to be called in place of the default <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method. The <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method takes no arguments and should return a string. The <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method you create can be any value you want, but it will be most useful if it carries information about the object.</zparagraph>
</FONT>
<P>

<A NAME="1193455"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The following code defines the <FONT FACE="courier, couriernew, monospaced size">Dog</FONT> object type and creates <FONT FACE="courier, couriernew, monospaced size">theDog,</FONT> an object of type <FONT FACE="courier, couriernew, monospaced size">Dog</FONT>:</zparagraph>
</FONT>
<P>
<A NAME="1193456"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>function Dog(name,breed,color,sex) {<br>
&nbsp;&nbsp;&nbsp;this.name=name<br>
&nbsp;&nbsp;&nbsp;this.breed=breed<br>
&nbsp;&nbsp;&nbsp;this.color=color<br>
&nbsp;&nbsp;&nbsp;this.sex=sex<br>
}
</zcodeline>
</FONT>
<P><A NAME="1193457"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>theDog = new Dog("Gabby","Lab","chocolate","girl")
</zcodeline>
</FONT>
<P>
<A NAME="1193458"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>If you call the <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method on this custom object, it returns the default value inherited from <FONT FACE="courier, couriernew, monospaced size">Object</FONT>:</zparagraph>
</FONT>
<P>
<A NAME="1203749"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>theDog.toString() //returns [object Object]
</zcodeline>
</FONT>
<P>
<A NAME="1203735"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The following code creates <FONT FACE="courier, couriernew, monospaced size">dogToString,</FONT> the function that will be used to override the default <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method. This function generates a string containing each property, of the form <FONT FACE="courier, couriernew, monospaced size">"property = value;"</FONT>.</zparagraph>
</FONT>
<P>
<A NAME="1193459"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>function dogToString() {<br>
&nbsp;&nbsp;&nbsp;var ret = "Dog " + this.name + " is [\n"<br>
&nbsp;&nbsp;&nbsp;for (var prop in this)<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ret += "  " + prop + " is " + this[prop] + ";\n"<br>
&nbsp;&nbsp;&nbsp;return ret + "]"<br>
}
</zcodeline>
</FONT>
<P>
<A NAME="1193460"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The following code assigns the user-defined function to the object's <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method:</zparagraph>
</FONT>
<P>
<A NAME="1193461"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>Dog.prototype.toString = dogToString
</zcodeline>
</FONT>
<P>
<A NAME="1193462"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>With the preceding code in place, any time <FONT FACE="courier, couriernew, monospaced size">theDog</FONT> is used in a string context, JavaScript automatically calls the <FONT FACE="courier, couriernew, monospaced size">dogToString</FONT> function, which returns the following string:</zparagraph>
</FONT>
<P>
<A NAME="1203804"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>Dog Gabby is [<br>
&nbsp;&nbsp;name is Gabby;<br>
&nbsp;&nbsp;breed is Lab;<br>
&nbsp;&nbsp;color is chocolate;<br>
&nbsp;&nbsp;sex is girl;<br>
]
</zcodeline>
</FONT>
<P>
<A NAME="1203805"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>An object's <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method is usually invoked by JavaScript, but you can invoke it yourself as follows:</zparagraph>
</FONT>
<P>
<A NAME="1193465"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>var dogString = theDog.toString()
</zcodeline>
</FONT>
<P><BR>
<A NAME="1193466"> </A>
<A NAME="Backward Compatibility"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zrefheader>Backward Compatibility</zrefheader>
</B>
</FONT>
<BR>
<P>
<A NAME="1193467"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zheadrunin>JavaScript 1.2. </zheadrunin>
</B>
</FONT>

<A NAME="1193468"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The behavior of the <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method depends on whether you specify <FONT FACE="courier, couriernew, monospaced size">LANGUAGE="JavaScript1.2"</FONT> in the <FONT FACE="courier, couriernew, monospaced size">&lt;SCRIPT&gt;</FONT> tag:</zparagraph>
</FONT>
<P>
<ul>
<A NAME="1193469"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>  <li></B>
<zsmartlist1>If you specify <FONT FACE="courier, couriernew, monospaced size">LANGUAGE="JavaScript1.2"</FONT> in the <FONT FACE="courier, couriernew, monospaced size">&lt;SCRIPT&gt;</FONT> tag, the <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method returns an object literal.</zsmartlist1>
</FONT>
<P><A NAME="1193470"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>  <li></B>
<zsmartlist1>If you do not specify <FONT FACE="courier, couriernew, monospaced size">LANGUAGE="JavaScript1.2"</FONT> in the <FONT FACE="courier, couriernew, monospaced size">&lt;SCRIPT&gt;</FONT> tag, the <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method returns <FONT FACE="courier, couriernew, monospaced size">[object </FONT><FONT FACE="courier, couriernew, monospaced size"><I>type</I></font><FONT FACE="courier, couriernew, monospaced size">]</FONT>, as with other JavaScript versions.</zsmartlist1>
</FONT>
<P></ul>
<BR>
<A NAME="1193471"> </A>
<A NAME="Examples"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zrefheader>Examples</zrefheader>
</B>
</FONT>
<BR>

<A NAME="1193472"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><B>Example 1: The location object.</B> The following example prints the string equivalent of the current location.</zparagraph>
</FONT>
<P>
<A NAME="1193473"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>document.write("location.toString() is " + location.toString() + "&lt;BR&gt;")
</zcodeline>
</FONT>
<P>
<A NAME="1193474"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The output is as follows:</zparagraph>
</FONT>
<P>
<A NAME="1195036"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>location.toString() is file:///C|/TEMP/myprog.htmll
</zcodeline>
</FONT>
<P>
<A NAME="1195040"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><B>Example 2: Object with no string value.</B> Assume you have an <FONT FACE="courier, couriernew, monospaced size">Image</FONT> object named <FONT FACE="courier, couriernew, monospaced size">sealife</FONT> defined as follows:</zparagraph>
</FONT>
<P>
<A NAME="1193480"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>&lt;IMG NAME="sealife" SRC="images\seaotter.gif" ALIGN="left" VSPACE="10"&gt;
</zcodeline>
</FONT>
<P>
<A NAME="1193484"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Because the <FONT FACE="courier, couriernew, monospaced size">Image</FONT> object itself has no special <FONT FACE="courier, couriernew, monospaced size">toString</FONT> method, <FONT FACE="courier, couriernew, monospaced size">sealife.toString()</FONT> returns the following:</zparagraph>
</FONT>
<P>
<A NAME="1193485"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>[object Image]
</zcodeline>
</FONT>
<P>
<A NAME="1193486"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><B>Example 3: The radix parameter.</B> The following example prints the string equivalents of the numbers 0 through 9 in decimal and binary.</zparagraph>
</FONT>
<P>
<A NAME="1193487"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>for (x = 0; x &lt; 10; x++) {<br>
&nbsp;&nbsp;&nbsp;document.write("Decimal: ", x.toString(10), " Binary: ",<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;x.toString(2), "&lt;BR&gt;")<br>
}
</zcodeline>
</FONT>
<P>
<A NAME="1193488"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The preceding example produces the following output:</zparagraph>
</FONT>
<P>
<A NAME="1193489"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>Decimal: 0 Binary: 0<br>
Decimal: 1 Binary: 1<br>
Decimal: 2 Binary: 10<br>
Decimal: 3 Binary: 11<br>
Decimal: 4 Binary: 100<br>
Decimal: 5 Binary: 101<br>
Decimal: 6 Binary: 110<br>
Decimal: 7 Binary: 111<br>
Decimal: 8 Binary: 1000<br>
Decimal: 9 Binary: 1001
</zcodeline>
</FONT>
<P><BR>
<A NAME="1193490"> </A>
<A NAME="See also"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zrefheader>See also</zrefheader>
</B>
</FONT>
<BR>

<A NAME="1193497"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><A HREF="object.html#1193320"  >Object.toSource</A>, <A HREF="object.html#1193540"  >Object.valueOf</A></zparagraph>
</FONT>
<P>
<BR>
<P>
<A NAME="1193499"> </A>
<A NAME="unwatch"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="4">
<B>
<zrefhead2>unwatch</zrefhead2>
</B>
</FONT>
<P>

<A NAME="1193516"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Removes a watchpoint set with the <A HREF="object.html#1193628"  >watch</A> method.<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="1193506"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext><I>Method of</I></ztabletext>
</FONT>&nbsp;</TD>
    <TD VALIGN=TOP>
<P>
<A NAME="1193511"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext><A HREF="object.html#1193136"  >Object</A></ztabletext>
</FONT>&nbsp;</TD>
  </TR>
  <TR>
    <TD VALIGN=TOP>
<P>
<A NAME="1193513"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext><I>Implemented in</I></ztabletext>
</FONT>&nbsp;</TD>
    <TD VALIGN=TOP>
<P>
<A NAME="1193515"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext>JavaScript 1.2, NES 3.0</ztabletext>
</FONT>&nbsp;</TD>
  </TR>
</TABLE>



<P></zparagraph>
</FONT>
<P>
<BR>
<A NAME="1193517"> </A>
<A NAME="Syntax"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zrefheader>Syntax</zrefheader>
</B>
</FONT>
<BR>
<A NAME="1193518"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>unwatch(<I>prop</I>)
</zcodeline>
</FONT>
<P><BR>
<A NAME="1193519"> </A>
<A NAME="Parameters"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>
<zrefheader>Parameters</zrefheader>
</B>
</FONT>
<BR>

<A NAME="1193525"> </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>
<P>
<A NAME="1193522"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext><FONT FACE="courier, couriernew, monospaced size">prop</FONT></ztabletext>
</FONT>&nbsp;</TD>
    <TD VALIGN=TOP>
<P>
<A NAME="1193524"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<ztabletext>The name of a property of the object.</ztabletext>
</FONT>&nbsp;</TD>