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Error Handling kya hota hai?

Error Handling ka matlab hota hai ki jab aapke JavaScript code mein koi error ya bug aata hai, to usse gracefully handle karna.

Error Handling ek technique hoti hai jo humein JavaScript code mein hone wale errors ko detect karne, samajhne aur unhe handle karne mein madad karti hai. Jab program run hota hai aur koi unexpected problem ya bug aata hai, to Error Handling use handle karne ke liye try, catch, finally blocks ka use kiya jata hai.

• try block mein wo code likha jata hai jahan error aane ki possibility hoti hai.
• Agar error hota hai, to control catch block mein chala jata hai jahan hum error ko handle karte hain.
• finally block hamesha chalta hai, chahe error aaye ya nahi.

Error Handling se program crash hone se bachta hai aur user ko better experience milta hai.

JavaScript mein error handling kaise hoti hai?

JavaScript mein error handling ka matlab hai code mein hone wale errors ko sahi tareeke se pakadna aur unka solution dena. Iske liye mainly try, catch, aur finally blocks ka use hota hai. try block mein wo code likha jata hai jisme error ho sakta hai, catch block error ko handle karta hai, aur finally block hamesha execute hota hai, chahe error aaye ya nahi. Yeh system code ko crash hone se bachata hai aur user experience improve karta hai.

• try
• catch
• finally

try block :

try block mein aap wo code likhte hain jo error generate kar sakta hai.
Agar try block ke andar koi error aata hai, to JavaScript turant catch block ko execute karta hai.
Agar koi error nahi aata, to catch block skip ho jata hai.

try {
  // Code that may throw an error
  let a = 10;
  console.log(a.toUpperCase()); // Error: a is not a string
}

catch block :

catch block tab chalta hai jab try block mein koi error hoti hai.
Yahan aap error ko handle, log ya user ko friendly message de sakte ho.
catch(error) mein error ek object hota hai jisme error ka details hota hai.

try {
  let x = undefinedVariable; // yeh variable exist nahi karta
} catch (error) {
  console.log("Error aayi hai: " + error.message);
}

Output: Error aayi hai: undefinedVariable is not defined.

Finally block

finally block hamesha execute hota hai, chahe try block mein error aaye ya na aaye.
Yahan aap clean-up code likh sakte ho, jaise: connection close karna, file band karna, etc.

try {
  let a = 5;
  let b = a.toUpperCase(); // error
} catch (error) {
  console.log("Error: " + error.message);
} finally {
  console.log("Yeh finally block hamesha chalega.");
}

Output :
Error: a.toUpperCase is not a function
Yeh finally block hamesha chalega.

Summary :

Example with Explanation :

function divide(a, b) {
  try {
    if (b === 0) {
      throw new Error("Zero se divide nahi kar sakte.");
    }
    console.log("Result: " + (a / b));
  } catch (error) {
    console.log("Caught Error: " + error.message);
  } finally {
    console.log("Operation complete.");
  }
}

divide(10, 0);

Explanation:

• b === 0 hone par humne manually ek error throw ki.
• catch ne us error ko pakda aur message diya.
• finally hamesha chala.

Output:
Caught Error: Zero se divide nahi kar sakte.
Operation complete.

Advanced: throw keyword kya karta hai?

Aap apne code mein manually bhi error throw kar sakte ho using throw:
Isse aap apne hisaab se koi bhi error bana sakte ho.

Bonus Tips:

• try-catch ka use tabhi karo jab aapko pata ho ki koi risky operation hai.
• API call, File handling, JSON parsing, etc. mein error handling bahut zaroori hai.
• finally ka use cleanup ke liye best hai.

Quiz: Test Your Knowledge on JavaScript Error Handling

Bonus: Practical Application!

Aaj hi JavaScript mein error handling ka istemal karke dekhein!

JavaScript error handling ko sahi tareeke se samajhne ke liye try, catch, finally, aur throw jaise keywords ka upayog karein. Inka istemal karke aap apne code ko zyada robust aur bug-free bana sakte hain.