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Page 7 of 7
<HTML><HEAD>
<TITLE>Color Database</TITLE>
<SCRIPT LANGUAGE="JavaScript">
Idx = new Object();
Data = new Object();
Idx[0]=10
Idx[1]="aliceblue"
Idx[2]="antiquewhite"
Idx[3]="aqua"
Idx[4]="aquamarine"
Idx[5]="azure"
Idx[6]="beige"
Idx[7]="bisque"
Idx[8]="black"
Idx[9]="blanchedalmond"
Idx[10]="blue"
Data[1]="f0f8ff"
Data[2]="faebd7"
Data[3]="00ffff"
Data[4]="7fffd4"
Data[5]="f0ffff"
Data[6]="f5f5dc"
Data[7]="ffe4c4"
Data[8]="000000"
Data[9]="ffebcd"
Data[10]="0000ff"
function checkDatabase() {
var Found = false;
var Item = document.testform.color.value.toLowerCase();
for (Count = 1; Count <= Idx[0]; Count++) {
if (Item == Idx[Count]) {
Found = true;
alert ("The hex triplet for '" + Item + "' is #" +
Data[Count]);
break;
}
}
if (! Found)
alert ("Sorry, the color '" + Item +"' is not listed in the database.");
}
</SCRIPT>
<FORM NAME="testform" onSubmit="checkDatabase()">
Specify a color name, then click the "Find" button to see its hex triplet: <BR>
<INPUT TYPE="text" NAME="color" Value="" onClick=0> <P>
<INPUT TYPE="button" NAME="button" Value="Find" onClick="checkDatabase()">
</FORM>
</BODY></HTML>
JavaScript's associative arrays can come in handy when creating databases. Associative array names are synonymous with the object's property names. With this feature you can simplify the color database script by defining a single object -- named Idx -- for the colors. Then use the names of the colors as the property names, defined as Idx["colorname"]. Each property is assigned the equivalent hexadecimal color value. For example, the property Idx["aliceblue"] -- which is the functional equivalent to the syntax Idx.aliceblue -- is assigned the hex value f0f8ff.
In the revised color database example, the user types a color name, which doubles as a property name for the Idx object. An
if expression determines whether the Idx object contains a property with that name. If the return value is "<undefined>" then
no such property exists, and therefore the color is not listed in the database. If the value is something else, it is assumed
to be the hex value of the specified color, and that value is displayed in an alert box.
<HTML>
<HEAD>
<TITLE>Another Color Database</TITLE>
<SCRIPT LANGUAGE="JavaScript">
Idx = new Object();
Idx["aliceblue"] = "f0f8ff"
Idx["antiquewhite"] ="faebd7"
Idx["aqua"] ="00ffff"
Idx["aquamarine"] ="7fffd4"
Idx["azure"] ="f0ffff"
Idx["beige"] ="f5f5dc"
Idx["bisque"] ="ffe4c4"
Idx["black"] ="000000"
Idx["blanchedalmond"] ="ffebcd"
Idx["blue"] ="0000ff"
function checkDatabase() {
var Item = document.testform.color.value.toLowerCase();
if ("" + Idx[Item] == "<undefined>")
alert ("Sorry, the color '" + Item +"' is not listed in the database.");
else
alert (Idx[Item])
}
</SCRIPT>
<FORM NAME="testform" onSubmit="checkDatabase()">
Specify a color name, then click the "Find" button to see its hex triplet: <BR>
<INPUT TYPE="text" NAME="color" Value="" onClick=0> <P>
<INPUT TYPE="button" NAME="button" Value="Find" onClick="checkDatabase()">
</FORM>
</BODY></HTML>
At first blush, JavaScript's army of objects can be dizzying. But many of these objects are highly specialized, and seldom used in a the typical JavaScript application. JavaScript's built-in objects are a different breed. Because they do not depend on the content of any given page, JavaScript's built-in objects -- Date, Math, String, Array, and Object -- tend to be heavily used in most any script. Mastery of these objects goes a long way to writing the coolest JavaScript applications possible.
Read more about Tools & Methods in JavaWorld's Tools & Methods section.