if...else Statement
Conditionally executes a group of statements, depending on the value of an expression.
if (condition)
statement1
[else
statement2]
- condition
-
Required. A Boolean expression. If condition is null or undefined, condition is treated as false.
- statement1
-
Required. The statement to be executed if condition is true. Can be a compound statement.
- statement2
-
Optional. The statement to be executed if condition is false. Can be a compound statement.
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 not 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.