JavaScript Errors
JavaScript Errors
In JavaScript Errors when something goes wrong while the program runs. They help you detect bugs and fix them.
JavaScript errors fall into two main categories:
Syntax Errors
These happen when the code violates JS rules.
Example:
Output:
Runtime Errors
These occur while the code is running.
Example:
Output:
Logical Errors
The code runs but produces unexpected results.
Example:
Result is incorrect, but no error message occurs.
Common JavaScript Error Types
| Error Type | Meaning | Example |
|---|---|---|
| ReferenceError | Using a variable that doesn’t exist | console.log(a); |
| SyntaxError | Code grammar error | if (true {} |
| TypeError | Wrong operation on a data type | "hello"() |
| RangeError | Value out of allowed range | .repeat(-1) |
| URIError | Invalid URL encoding | decodeURI("%") |
| EvalError | Issues with eval() function (rare) | eval("break") |
Handling Errors with try...catch
It allows handling errors using try, catch, and optionally finally.
Output:
Adding finally Block
The finally block always executes, whether an error happens or not.
Throwing Custom Errors
You can create your own error messages with throw.
Output:
Checking Error Name and Message
Summary
| Feature | Meaning |
|---|---|
| Js errors help find mistakes | Yes |
| Different types: Syntax, Runtime, Logical | Yes |
Use try...catch to avoid breaking program | Yes |
| You can throw custom errors | Yes |
