if...else Statement

See Also

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, because there is more than one statement between the if and else statements. Braces are required around the statements between if and else.