ELSE

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Javascript Reserved Word – ELSE

ELSE is part of the IF.

ELSE can be used to have some javascript code run as a condition
other than the main stream logic (expression) in the IF statement.



The basic syntax for an ELSE statement:






if (expression)


[{ [code;]+ }] | [code;]

else
[{ [code;]+ }] | [code;]




You should already be fimilar with the IF logic.
This ELSE allows you to have code run when the expression in the IF
equates to a boolean false value.


Expressions that evaluate to a boolean false value are:


undefined, null, 0, false


All other things equate to a boolean true statement.



Very simple ELSE usage where these all output “It was False”:




if (!1)
document.write(“It was True”);
else
document.write(“It was False”);
Note that “!” is “not” – so “not one” equates to boolean false.

if (0)
document.write(“It was True”);
else
document.write(“It was False”);

if (1 != 1)
document.write(“It was True”);
else
document.write(“It was False”);

Note that “!=” is the “is it not equal to” condition.



It follows that any complexity of the expression in the IF statement still results
in a boolean value. When it is false, the ELSE portion will run.



The last part to mention about ELSE’s is the ELSE IF:


if (!1) document.write(“!1”);

else if (!2) document.write(“!2”);

else if (!0) document.write(“!0”);

else document.write(“There were all false.”):


This will output “!0” as this is the first boolean expression that evaluated to TRUE.



ELSEs associate with the nearest if that it can see in its scope.

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