JavaScript Conditionals
Conditional Statements
When you write code, you often want to perform different actions for different conditions.
Conditional statements run different code depending on a true or false condition.
Conditional statements include:
- if
- if...else
- if...else if...else
- switch
- ternary (? :)
When to use Conditionals
-
Use
ifto specify a code block to be executed, if a specified condition istrue -
Use
elseto specify a code block to be executed, if the same condition isfalse -
Use
else ifto specify a new condition to test, if the first condition isfalse -
Use
switchto specify many alternative code blocks to be executed -
Use
(? :)(ternary) as a shorthand forif...else
The if Statement
Use if to specify a code block to be executed,
if a specified condition is true.
Syntax
if (condition) {
// code to execute if the condition is true
}
// code to execute if the condition is true
}
The else Statement
Use else to specify a code block to be executed,
if the same condition is false.
Syntax
if (condition) {
// code to execute if the condition is true
} else {
// code to execute if the condition is false
}
// code to execute if the condition is true
} else {
// code to execute if the condition is false
}
The else if Statement
Use else if to specify a new condition to test,
if the first condition is false.
Syntax
if (condition1) {
// code to execute if condition1 is true
} else if (condition2) {
// code to execute if the condition1 is false and condition2 is true
} else {
// code to execute if the condition1 is false and condition2 is false
}
// code to execute if condition1 is true
} else if (condition2) {
// code to execute if the condition1 is false and condition2 is true
} else {
// code to execute if the condition1 is false and condition2 is false
}
The switch Statement
Use switch to specify many alternative code blocks
to be executed.
Syntax
switch(expression) {
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}
Ternary Operator (? :)
Use (? :) (ternary) as a shorthand for
if...else.
Example
condition ? expression1 : expression2