JS-Array of Objects Questions

 let studentRecords = [ {name: 'John', id: 123, marks : 98 }, {name: 'Baba', id: 101, marks : 23 }, {name: 'yaga', id: 200, marks : 45 }, 
{name: 'Wick', id: 115, marks : 75 } ];

Capitalize values.

We are interested in retrieving only the name of the students and all the names should be in caps. e.g: ['JOHN', 'BABA', 'YAGA', 'WICK']

Code:-

let names = studentRecords.map(({name}) => name.toUpperCase());
console.log(names);

Conditions for AOO.

Suppose we have the same dataset as above but this time we want to get the details of students who scored more than 50 marks.
e.g: [{name: 'John', id: 123, marks : 98 },{name: 'Wick', id: 115, marks : 75 }].

Code:-

const newArr = studentRecords.map(({name, id, marks}) => {
    if(marks > 50){
        console.log({name, id, marks});
    }
});

Multiple conditions for AOO.

Retrieve the details of students who scored more than 50 marks and have id greater than 120.

Code:-

const newArr = studentRecords.map(({name, id, marks}) => {
    if(marks > 50 && id > 120){
        console.log({name, id, marks});
    }
});

Summing up values.

Consider the same scenario we have discussed above, but this time we would like to know the sum total of the marks of all students.

Code:-

var sum = 0;
    let markSum = studentRecords.forEach(({marks}) => {
    	sum = sum + marks;
    	return sum;
    });
console.log(sum);

More than 50.

This time we want to get only the names of the students who scored more than 50 marks from the same dataset used above.

Code:-

let names = studentRecords.map(({name, marks}) =>{
    if(marks > 50){
    	console.log({name})
    }
});

Condition on AOO.

This time we are required to print the sum of marks of the students with id > 120.

Output:-

var sum = 0;
    let markSum = studentRecords.forEach(({marks, id}) => {
    	if(id >= 120){
    		sum = sum + marks;
    		return sum;
    	}
    });
console.log(sum);

Passed with grace.

This time we are required to print the total marks of the students with marks greater than 50 after a grace of 15 marks has been added to those students who scored less than 50.

Code:-

var sum = 0;
    var newmarks = 0;
    let markSum = studentRecords.forEach(({marks, id}) => {
    		newmarks = marks + 15;
    		if(newmarks >= 50){
    			sum = sum + newmarks;
    			return sum;
    		}
    });
console.log(sum-30);

Create Array with Objects.

Create 6 objects , each object will have name, class, roll no as properties. Store these objects in an array of objects.

Code:-

let student2 = {"name":"stu2", "class":"1st", "rollNo":"12"};
let student3 = {"name":"stu3", "class":"2nd", "rollNo":"21"};
let student4 = {"name":"stu4", "class":"2nd", "rollNo":"22"};
let student5 = {"name":"stu5", "class":"3rd", "rollNo":"31"};

const students = [{"name":"stu1", "class":"1st", "rollNo":"11"}];

students.push(student2, student3, student4, student5);

students.push({"name":"stu6", "class":"4th", "rollNo":"41"})

console.log(students)