<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>Title</title></head><body><script> var studentsArray = [ { "rollnumber": 1, "name": "dj", "subject": "physics" }, { "rollnumber": 2, "name": "tanmay", "subject": "biology" }, { "rollnumber": 3, "name": "amit", "subject": "chemistry" } ]; function functiontofindIndexByKeyValue(arraytosearch, key, valuetosearch) { for (var i = 0; i < arraytosearch.length; i++) { if (arraytosearch[i][key] == valuetosearch) { return i; } } return null; } var index = functiontofindIndexByKeyValue(studentsArray, "rollnumber", 3); console.log(index);</script></body></html> 
