Language Java Script Definitive Examples 9.4.TXT

 <!-- This example is from the book _JavaScript: The Definitive Guide_.     -->
<!-- Written by David Flanagan.  Copyright (c) 1996 O'Reilly & Associates. -->
<!-- This example is provided WITHOUT WARRANTY either expressed or implied.-->
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<SCRIPT LANGUAGE="JavaScript">
// Determining whether strings are compared by value or reference is easy.
// We compare two clearly distinct strings that happen to contain the same
// characters.  If they are compared by value they will be equal, but if they
// are compared by reference, they will not be equal:
s1 =index.html "hello";
s2 = "hell" + "o";
if (s1 == s2) document.write("Strings compared by value");

// Determining whether functions are compared by value or reference is trickier
// because we cannot define two functions with the same name.  Therefore, we
// have to use unnamed functions.  Don't feel you have to understand this code.
// We create two distinct functions that contain exactly the same code.
// If JavaScript says these two functions are equal, then functions are 
// compared by value, otherwise they are compared by reference
F = new Function("return 1;"); // F and G are Function objects that contain
G = new Function("return 1;"); //    unnamed function values.
f = F.valueOf();               // Convert F and G to the actual function values
g = G.valueOf();
if (f == g)                    // now compare them
    document.write("Functions compared by value");
</SCRIPT>

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