let students = [];

for (let i = 1; i <= 10; i++) {
      students.push({
                Id: i,
                Name: "Student" + i,
                Roll: "100" + i
      });
}

Use of .map() :

 let useMap = students.map(x=>x.Roll == 1004);

Output : 

Use of .map() with .filter() : 

let useMapWithFilter = students.map(x=>x.Roll == 1004 ? x : null).filter(n=>n);

Output : 
Use of .find() :

let useFind = students.find(x=>x.Roll == 1004);

Output : 

Use of .filter() :

let usefilter = students.filter(x => x.Roll == 1004);

Output : 
N.B : .find() is faster then .filter() and .reduce()

Use of .findIndex() :

let useFindIndex = students.findIndex(x => x.Roll == 1004);

Output :  3