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Microsoft® JScript™
if...else Statement
 Language Reference 
Version 1 

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Description
Conditionally executes a group of statements, depending on the value of an expression.
Syntax
if (condition)
     statement1
[else
     statement2]

The if...else statement syntax has these parts:

Part Description
condition A Boolean expression. If condition is null or undefined, condition is treated as false.

statement1 The statement to be executed if condition is true. Can be a compound statement.
statement2 The statement to be executed if condition is false. Can be a compound statement.

Remarks
It is generally good practice to enclose statement1 and statement2 in braces ({}) for clarity and to avoid inadvertent errors. In the following example, you may intend that the else be used with the first if statement, but it is used with the second one.
if (x == 5)
  if (y == 6)
     z = 17;
else
  z = 20;
Changing the code in the following manner eliminates any ambiguities:
if (x == 5)
  {
  if (y == 6)
     z = 17;
  }
else
  z = 20;

Similarly, if you want to add a statement to statement1, and you don't use braces, you can accidentally create an error:

if (x == 5)
  z = 7;
  q = 42;
else
  z = 19;
In this case, there is a syntax error, as there is more than one statement between the if and else statements. Putting braces around the statements between the if and else is required.


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