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Is it a good practice to end switch with defaults in JavaScript?
In this tutorial, we will learn if it is a good practice to end switch with defaults in JavaScript.
In JavaScript, we generally use the if or if-else statements if we need to check any conditions. Still, if we need to check multiple conditions for an expression, it becomes very complex and unorganized, so we use the switch statements for that situation.
The switch statement compares the value of an expression to a series of case clauses, then executes statements after the first case clause that matches the value, and so on, until a break statement is met. If no case matches the value of the expression, the switch statement's default case is executed.
Syntax
switch (expression) {
case value1:
// code block if the expression matches the value1
break
case value2:
// code block if the expression matches the value2
break
...
default:
// code block if expression not matches any values
}
The above syntax shows the switch statement's different cases, break statements, and default statements.
It is a question that arrives to many JavaScript developers: Is it good practice to end switch statements with a default clause or not? But before directly jumping to the conclusion, let's see what behavior the switch statement shows with and without the default clause.
Example 1: Switch Statement Without Default Case
In the below example, we have used the switch in JavaScript without the default. We use an array of result grades and pass each grade in the switch statement to show the original meaning of these grades. For example, the grade "O" will show "Outstanding". A button "Show" is associated with a click event that executes a function whenever a user clicks on it. This function loops through each grade and outputs its corresponding meaning in the webpage using a switch statement.
<html>
<body>
<h2>Using the <i>switch statement without default</i> in JavaScript</h2>
<button onclick="show()"> Show </button>
<div
id="root"
style="border: 1px solid gray; margin: 5px 0px; padding: 5px">
</div>
<script>
// Grades array
const grades = ['O', 'A', 'F', 'Z']
// root element
const root = document.getElementById('root')
// Showing grades in the webpage
grades.map((grade) => {
root.innerHTML += grade + '<br /> <br/>'
})
// 'Show' button click event handler function
function show() {
root.innerHTML = '';
grades.map((grade) => {
// switch statement
switch (grade) {
case 'O':
root.innerHTML += grade + ' = Outstanding!' + '<br /> <br/>'
break
case 'A':
root.innerHTML += grade + ' = Good!' + '<br /> <br/>'
break
case 'F':
root.innerHTML += grade + ' = Fail!' + '<br /> <br/>'
break
}
})
}
</script>
</body>
</html>
So we can see if the expression did not match with any of the cases, then the switch statement did not run any code corresponding to it. Hence undesired output can arrive. In this case, the 'Z' grade is missing on the webpage after clicking the button.
Example 2: Switch Statement With Default Case
In the example below, we will use the same example as the previous one, but this time, we will use the switch statement with the default clause and compare the two outputs.
<html>
<body>
<h2>Using the <i>switch statement with default</i> in JavaScript</h2>
<button onclick="show()"> Show </button>
<div
id="root"
style="border: 1px solid gray; margin: 5px 0px; padding: 5px">
</div>
<script>
// Grades array
const grades = ['O', 'A', 'F', 'Z']
// root element
const root = document.getElementById('root')
// Showing grades in the webpage
grades.map((grade) => {
root.innerHTML += grade + '<br /> <br/>'
})
// 'Show' button click event handler function
function show() {
root.innerHTML = ''
grades.map((grade) => {
// switch statement
switch (grade) {
case 'O':
root.innerHTML += grade + ' = Outstanding!' + '<br /> <br/>'
break
case 'A':
root.innerHTML += grade + ' = Good!' + '<br /> <br/>'
break
case 'F':
root.innerHTML += grade + ' = Fail!' + '<br /> <br/>'
break
default:
root.innerHTML += grade + ' = Unknown Grade!' + '<br /> <br/>'
}
})
}
</script>
</body>
</html>
Benefits of Using Default Case
The default case provides several advantages:
- Error Handling: Catches unexpected values that don't match any case
- Code Reliability: Prevents silent failures when input doesn't match expected values
- Debugging: Makes it easier to identify when unexpected values are processed
- User Experience: Provides feedback for invalid or unknown inputs
Best Practices
| Approach | Handles Unexpected Values | Code Safety | Recommended |
|---|---|---|---|
| Without default | No - silent failure | Low | No |
| With default | Yes - explicit handling | High | Yes |
Conclusion
It is definitely a good practice to end switch statements with a default case in JavaScript. The default clause ensures that unexpected values are handled gracefully, making your code more robust and preventing silent failures that could lead to bugs.
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