object.html

javascript 1.5规范

<A NAME="1193243"> </A>
<A NAME="Description"> </A>
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<zrefheader>Description</zrefheader>
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<A NAME="1193244"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>All objects inherit a <FONT FACE="courier, couriernew, monospaced size">constructor</FONT> property from their <FONT FACE="courier, couriernew, monospaced size">prototype</FONT>:</zparagraph>
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<A NAME="1193245"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>o = new Object  // or o = {} in JavaScript 1.2<br>
o.constructor == Object<br>
a = new Array   // or a = [] in JavaScript 1.2<br>
a.constructor == Array<br>
n = new Number(3)<br>
n.constructor == Number
</zcodeline>
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<A NAME="1193246"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Even though you cannot construct most HTML objects, you can do comparisons. For example,</zparagraph>
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<A NAME="1193247"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>document.constructor == Document<br>
document.form3.constructor == Form
</zcodeline>
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<A NAME="1193248"> </A>
<A NAME="Examples"> </A>
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<zrefheader>Examples</zrefheader>
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<A NAME="1193249"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The following example creates a prototype, <FONT FACE="courier, couriernew, monospaced size">Tree</FONT>, and an object of that type, <FONT FACE="courier, couriernew, monospaced size">theTree</FONT>. The example then displays the <FONT FACE="courier, couriernew, monospaced size">constructor</FONT> property for the object <FONT FACE="courier, couriernew, monospaced size">theTree</FONT>.</zparagraph>
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<A NAME="1193250"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>function Tree(name) {<br>
&nbsp;&nbsp;&nbsp;this.name=name<br>
}<br>
theTree = new Tree("Redwood")<br>
document.writeln("&lt;B&gt;theTree.constructor is&lt;/B&gt; " +<br>
&nbsp;&nbsp;&nbsp;theTree.constructor + "&lt;P&gt;")
</zcodeline>
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<A NAME="1193251"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>This example displays the following output:</zparagraph>
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<A NAME="1193252"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>theTree.constructor is function Tree(name) { this.name = name; }
</zcodeline>
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<A NAME="1194118"> </A>
<A NAME="eval"> </A>
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<zrefhead2>eval</zrefhead2>
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<A NAME="1194131"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Deprecated. Evaluates a string of JavaScript code in the context of an object.<BR>
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<A NAME="1194121"> </A>
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<ztabletext><I>Method of</I></ztabletext>
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<A NAME="1194126"> </A>
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<ztabletext><A HREF="object.html#1193136"  >Object</A></ztabletext>
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<A NAME="1194128"> </A>
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<ztabletext><I>Implemented in</I></ztabletext>
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<A NAME="1194130"> </A>
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<ztabletext>JavaScript 1.1, NES 2.0</ztabletext>
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<A NAME="1195556"> </A>
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<ztabletext></ztabletext>
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<A NAME="1195557"> </A>
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<ztabletext>JavaScript 1.2, NES 3.0: deprecated as method of objects; retained as top-level function.</ztabletext>
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<A NAME="1203544"> </A>
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<ztabletext></ztabletext>
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<A NAME="1203565"> </A>
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<ztabletext>JavaScript 1.4: removed as method of objects.</ztabletext>
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<A NAME="1194132"> </A>
<A NAME="Syntax"> </A>
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<zrefheader>Syntax</zrefheader>
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<A NAME="1194133"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>eval(<I>string</I>)
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<A NAME="1194134"> </A>
<A NAME="Parameters"> </A>
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<zrefheader>Parameters</zrefheader>
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<A NAME="1194140"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><BR>
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<zcodeline>string
</zcodeline>
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<A NAME="1194139"> </A>
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<ztabletext>Any string representing a JavaScript expression, statement, or sequence of statements. The expression can include variables and properties of existing objects.</ztabletext>
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<A NAME="1194141"> </A>
<A NAME="Description"> </A>
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<zrefheader>Description</zrefheader>
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<A NAME="1194142"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The <FONT FACE="courier, couriernew, monospaced size">eval</FONT> method is no longer available as a method of <FONT FACE="courier, couriernew, monospaced size">Object</FONT>. Use the top-level <A HREF="toplev.html#1063795"  >eval</A> function.</zparagraph>
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<A NAME="1202533"> </A>
<A NAME="Backward Compatibility"> </A>
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<zrefheader>Backward Compatibility</zrefheader>
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<A NAME="1203587"> </A>
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<zheadrunin>JavaScript 1.2 and 1.3. </zheadrunin>
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<A NAME="1203588"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><FONT FACE="courier, couriernew, monospaced size">eval</FONT> as a method of Object and every object derived from Object is deprecated (but still available).</zparagraph>
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<A NAME="1202534"> </A>
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<zheadrunin>JavaScript 1.1. </zheadrunin>
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<A NAME="1202544"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><FONT FACE="courier, couriernew, monospaced size">eval</FONT> is a method of Object and every object derived from Object.</zparagraph>
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<A NAME="1194155"> </A>
<A NAME="See also"> </A>
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<zrefheader>See also</zrefheader>
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<A NAME="1194159"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><A HREF="toplev.html#1063795"  >eval</A></zparagraph>
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<A NAME="1193255"> </A>
<A NAME="prototype"> </A>
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<zrefhead2>prototype</zrefhead2>
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<A NAME="1193256"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Represents the prototype for this class. You can use the prototype to add properties or methods to all instances of a class. For more information, see <A HREF="function.html#1193426"  >Function.prototype</A>.<BR>
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<A NAME="1193262"> </A>
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<ztabletext><I>Property of</I></ztabletext>
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<A NAME="1193267"> </A>
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<ztabletext><A HREF="object.html#1193136"  >Object</A></ztabletext>
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<A NAME="1193269"> </A>
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<ztabletext><I>Implemented in</I></ztabletext>
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<A NAME="1193271"> </A>
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<ztabletext>JavaScript 1.1</ztabletext>
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<A NAME="1196486"> </A>
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<ztabletext><I>ECMA version</I></ztabletext>
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<A NAME="1196488"> </A>
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<ztabletext>ECMA-262</ztabletext>
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<A NAME="1193320"> </A>
<A NAME="toSource"> </A>
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<zrefhead2>toSource</zrefhead2>
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<A NAME="1193322"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Returns a string representing the source code of the object.<BR>
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<A NAME="1193325"> </A>
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<ztabletext><I>Method of</I></ztabletext>
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<A NAME="1193330"> </A>
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<ztabletext><A HREF="object.html#1193136"  >Object</A></ztabletext>
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<A NAME="1193332"> </A>
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<ztabletext><I>Implemented in</I></ztabletext>
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<A NAME="1193334"> </A>
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<ztabletext>JavaScript 1.3</ztabletext>
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<A NAME="1193335"> </A>
<A NAME="Syntax"> </A>
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<zrefheader>Syntax</zrefheader>
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<A NAME="1193336"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>toSource()
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<A NAME="1193337"> </A>
<A NAME="Parameters"> </A>
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<zrefheader>Parameters</zrefheader>
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<A NAME="1193338"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>None</zparagraph>
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<A NAME="1193339"> </A>
<A NAME="Description"> </A>
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<zrefheader>Description</zrefheader>
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<A NAME="1204221"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The <FONT FACE="courier, couriernew, monospaced size">toSource</FONT> method returns the following values:</zparagraph>
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<ul>
<A NAME="1204304"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>  <li></B>
<zsmartlist1>For the built-in <FONT FACE="courier, couriernew, monospaced size">Object</FONT> object, <FONT FACE="courier, couriernew, monospaced size">toSource</FONT> returns the following string indicating that the source code is not available:</zsmartlist1>
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<P><A NAME="1204317"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>&nbsp;&nbsp;&nbsp;function Object() {<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[native code]<br>
&nbsp;&nbsp;&nbsp;}
</zcodeline>
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<P><A NAME="1204308"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>  <li></B>
<zsmartlist1>For instances of <FONT FACE="courier, couriernew, monospaced size">Object</FONT>, <FONT FACE="courier, couriernew, monospaced size">toSource</FONT> returns a string representing the source code.</zsmartlist1>
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<P><A NAME="1204331"> </A>
<FONT FACE="Arial, Helvetica, sans-serif" SIZE="-1">
<B>  <li></B>
<zsmartlist1>For custom objects, <FONT FACE="courier, couriernew, monospaced size">toSource</FONT> returns the JavaScript source that defines the object as a string.</zsmartlist1>
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<P></ul>

<A NAME="1204183"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>This method is usually called internally by JavaScript and not explicitly in code. You can call <FONT FACE="courier, couriernew, monospaced size">toSource</FONT> while debugging to examine the contents of an object.</zparagraph>
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<A NAME="1193340"> </A>
<A NAME="Examples"> </A>
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<zrefheader>Examples</zrefheader>
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<A NAME="1204772"> </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>
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<A NAME="1204688"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="-1">
<zcodeline>function Dog(name,breed,color,sex) {<br>