XHR (XMLHttpRequest) ek browser API hai jo client-side JavaScript code ko server ke saath asynchronous communication (data exchange) karne ki facility deti hai bina page ko reload kiye. Iska main use dynamic content ko fetch karna hota hai jaise ki web pages ko update karna, data submit karna ya kisi bhi kind ka data server se lena aur user ko bina page reload ke dikhana.
Yeh ek important component hai AJAX (Asynchronous JavaScript and XML) ka, jo modern web applications mein commonly use hota hai, jaise ki Google Maps, Facebook, etc.
XHR ka kaam:
Request bhejna: Jab user koi action karta hai (jaise form submit karna), to JavaScript XHR ke through request send karta hai server ko.
Response receive karna: Server se response milne par, page ko bina reload kiye, JavaScript data ko process karta hai aur page ko update karta hai.
Example ke liye, jab aap kisi website pe login karte ho aur page reload nahi hota, toh ho sakta hai ki XHR use ho raha ho apne data ko background mein server se fetch karne ke liye.
Asynchronous Communication: Yeh synchronous aur asynchronous dono modes mein kaam kar sakta hai, lekin generally asynchronous mode hi use hota hai taaki user ko page reload ka experience na ho.
Data Formats: XHR JSON, XML, HTML ya plain text jaise multiple formats mein data exchange kar sakta hai.
In short, XHR ka use web applications ko fast aur dynamic banane ke liye hota hai.
Debugging ek process hai jisme aap apne code ko carefully examine karte hain taaki aap identify kar sakein aur fix kar sakein errors ya bugs jo code mein ho sakte hain. Jab code run nahi karta ya expected result nahi deta, toh debugging ka use hota hai taaki aap find out kar sakein ki code mein problem kahaan hai.
Debugging ke steps usually kuch is tarah hote hain:
Error Identify Karna: Sabse pehle aapko error ya issue ko identify karna hota hai. Yeh errors syntax errors (jaise galat likha gaya code) ya logical errors (jaise galat calculation) ho sakte hain.
Error Message Padna: Jab aapka code run karte waqt koi error aati hai, toh error message padna zaroori hota hai. Yeh message usually bataata hai ki error kis part mein hai.
Code ko Step-by-Step Execute Karna: Aap apne code ko step-by-step run karte hain, taaki dekh sakein ki kis part mein problem ho sakti hai. Isme aap breakpoints ka use karte hain (yeh ek aise points hote hain jahan pe execution temporarily rukta hai).
Testing and Fixing Errors: Jab aapko problem ka idea mil jata hai, toh usko fix karte hain aur phir se code ko run karke check karte hain ki fix kaam kar raha hai ya nahi.
Debugging Tools ka Use: Debugging ko efficient banane ke liye developers debugging tools ka use karte hain, jo error tracking, code inspection aur performance analysis mein madad karte hain. Tools jaise Visual Studio Code (VSCode), PyCharm, Chrome Developer Tools, etc. debugging ko aasaan bana dete hain.
Example: Agar aapne koi function likha hai jo numbers ko add karta hai, lekin aapko pata chalta hai ki result galat aa raha hai. Aap debugging ke through step-by-step dekhte ho ki kahin koi mistake toh nahi ho rahi, jaise ki addition ya variable ki value galat ho sakti hai.
Summary: Debugging basically ek problem-solving process hai jisme aap apne code ko carefully check karte ho, errors find karte ho, aur unhe fix karte ho.