User input is one of the biggest sources of security problems in web applications.
Whenever users type something into a form, search box, or URL, that data can be misused if it is not handled carefully.
Handling user input safely means validating, sanitizing, and controlling how data is used inside your JavaScript code.
Why Safe Input Handling Matters
- Prevents security attacks like XSS
- Stops invalid or harmful data
- Protects application logic
- Improves data quality
- Builds trust with users
Every professional developer treats user input as untrusted by default.
If a user enters harmful code instead of a name, it will be executed in the browser.
This opens the door to serious security issues.
textContent treats user input as plain text.
This prevents scripts or HTML from being executed.
These examples show how small changes can make user input much safer.
By validating input and displaying it securely, students gain the ability to protect their JavaScript applications from common attacks — a key skill for becoming a professional and job-ready developer.