diff --git a/content/javascript/concepts/input-validation/input-validation.md b/content/javascript/concepts/input-validation/input-validation.md new file mode 100644 index 00000000000..3d39627b7b6 --- /dev/null +++ b/content/javascript/concepts/input-validation/input-validation.md @@ -0,0 +1,65 @@ +--- +Title: 'Input Validation' +Description: 'Input validation is the process of checking whether the data provided by a user or application is valid and meets the expected criteria before processing it further.' +Keywords: + - input validation + - guard clause + - parameter validation + - error handling +--- + +# Input Validation + +Input validation is the process of checking whether data received from a user or external source is valid and meets the expected criteria before using it in an application. It's a critical security and reliability practice that helps prevent unexpected errors and protect against malicious input. + +## Why Input Validation Matters + +- **Error Prevention**: Catches invalid or unexpected data before it causes runtime errors +- **Security**: Protects against injection attacks and malicious input +- **Data Integrity**: Ensures the application works with clean, expected data +- **Better User Experience**: Provides clear feedback when input doesn't meet requirements + +## Common Validation Checks + +- **Empty/Null Checks**: Verify that required parameters are not empty or undefined +- **Type Checks**: Ensure data is of the expected type (string, number, array, etc.) +- **Length Checks**: Verify strings meet minimum/maximum length requirements +- **Format Checks**: Validate data matches expected patterns (email, phone, etc.) +- **Range Checks**: Ensure numbers are within acceptable minimum and maximum values + +## Example: Guard Clause for Empty Parameters + +A simple but effective validation approach is using a guard clause to check for empty or undefined input at the beginning of a function: + +```javascript +function parseContent(content) { + // Guard clause: validate input before processing + if (!content || content.trim() === '') { + throw new Error('Input content cannot be empty.'); + } + + // Safe to proceed with processing + return content.toUpperCase(); +} + +// Usage +try { + parseContent(''); // Throws error +} catch (error) { + console.error(error.message); // Output: Input content cannot be empty. +} +``` + +## Best Practices + +1. **Validate Early**: Check input at the entry point of your function or module +2. **Be Specific**: Provide clear, descriptive error messages that help users understand what went wrong +3. **Fail Fast**: Stop processing immediately when validation fails +4. **Document Requirements**: Clearly specify what constitutes valid input +5. **Consider Edge Cases**: Handle null, undefined, empty strings, and unexpected types + +## See Also + +- [Try-Catch](/javascript/concepts/try-catch/) +- [Error Handling](/javascript/concepts/errors/) +- [Functions](/javascript/concepts/functions/)