<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script>
const input = Number(prompt('Number : ', 'Number'))
switch (input % 2){
case 0:
alert('even')
break
case 1:
alert('odd')
break
default:
alert('not number')
break
}
</script>
</head>
<body>
</body>
</html>### Breakdown of the JavaScript Code
- `const input = Number(prompt('Number : ', 'Number'))`: This line displays a prompt dialog box asking the user to enter a number. The input is then converted to a number type using the `Number` constructor. If the input cannot be converted to a number, the result will be `NaN` (Not-a-Number).
- `switch (input % 2)`: The modulo operator (`%`) is used to get the remainder of the division of `input` by `2`. This operation helps determine if the number is even or odd. The result is used in a `switch` statement to match against different cases.
- `case 0`: If `input % 2` equals `0`, the number is even. An alert box with the message `'even'` is displayed.
- `case 1`: If `input % 2` equals `1`, the number is odd. An alert box with the message `'odd'` is displayed.
- `default`: The default case handles situations where the input is not an even or odd number, which includes `NaN` resulting from non-numeric inputs. It displays an alert box with the message `'not number'`.
### Execution Flow
1. When the document is loaded in a web browser, the user is immediately prompted to enter a number.
2. The user's input is converted to a number and evaluated to determine if it is even, odd, or not a number.
3. An alert box is displayed to the user indicating whether the entered number is even, odd, or not a number based on the input's evaluation.
### Considerations
- The use of the `Number` constructor ensures that non-numeric inputs result in `NaN`. The modulo operation with `NaN` will also yield `NaN`, which won't match `case 0` or `case 1` and thus will hit the `default` case.
- This script assumes that the user will input integer values. For floating-point numbers, the result of the modulo operation might not be strictly `0` or `1`, but the `default` case will handle any input that doesn't produce a `0` remainder for being even.
- The script is executed as soon as the page loads, which might not always be the desired behavior in a more complex application. For a more interactive application, this code could be wrapped in a function and called based on a specific event, like clicking a button.
'개념 > 혼자 공부하는 Javascript' 카테고리의 다른 글
| chapter 3) Using nested conditionals (0) | 2024.11.28 |
|---|---|
| chapter 3) Using conditional operators (0) | 2024.11.27 |
| chapter 3) Using if conditional statements (0) | 2024.11.25 |
| chapter 2) Example of using increment/decrement operators (0) | 2024.11.24 |
| chapter 2) Understanding ball expressions (0) | 2024.11.23 |