Error Handling Debugging and Strict Mode

Continue your JavaScript Tutorial learning path with hands-on explanation, code practice, and quiz.

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Course

JavaScript Tutorial

Estimated Time

8 min

Progress

30%

Track Position

22 / 73

Lesson Overview

Simple Explanation

try/catch runtime errors capture karta hai. Custom Error meaningful messages deta hai. debugger statement code execution pause karta hai (devtools me). Console methods debugging ke liye useful hain. strict mode silent bugs ko errors me convert karta hai.

Code Explanation

Custom ValidationError throw karke specific catch handling ki gayi hai.

Output Description

Invalid data par controlled error message print hoga.

Practice Exercise

Aisa function banao jo password length check kare aur custom error throw kare.

Extra Explanation

Why This Matters

Error Handling Debugging and Strict Mode is core to dynamic behavior. Strong fundamentals here help you build forms, API flows, and interactive UI with confidence.

Real-World Workflow

Complex features are usually split into small functions, then verified through focused logging and tiny test cases.

Common Mistakes to Avoid

Avoid uncontrolled globals, weak error handling, and ignored async states. Define clear input-output expectations for each function.

Example + Live Practice

<script>
  "use strict";

  class ValidationError extends Error {
    constructor(message) {
      super(message);
      this.name = "ValidationError";
    }
  }

  function parseAge(age) {
    if (age < 0) throw new ValidationError("Age cannot be negative");
    return age;
  }

  try {
    console.info("Parsing age...");
    debugger;
    console.log(parseAge(-1));
  } catch (error) {
    console.error(error.name, error.message);
  }
</script>

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