CODEWITHSUNDEEP
javascript
Rendy
Rendy

Reputation: 5698

Array push still using previous reference?

I have following code:

var students = [];
for(var i = 0; i < classes.length; i++) {
    var student = {};
    student = classes[i].student;
    student.teacher = classes[i].teacher;
    students.push(student);
}

Somehow the students will print same object for all its contents, although I have put var student = {}; inside the loop, thus it must not refer to same reference.

Anyone has idea why this happens?

Upvotes: 0

Views: 41

Answers (1)

nnnnnn
nnnnnn

Reputation: 150080

You put student = {} inside the loop, then on the line immediately following that one you overwrote that by assigning student = classes[i].student.

If the intention is to make a copy of whatever classes[i].student is you can use the Object.assign() method:

var student = Object.assign({}, classes[i].student);

In context:

var students = [];
for(var i = 0; i < classes.length; i++) {
    var student = Object.assign({}, classes[i].student);
    student.teacher = classes[i].teacher;
    students.push(student);
}

(Note that Object.assign() doesn't do a deep copy - I'm not sure if that matters because you haven't shown what the classes array structure is.)

You could also use the .map() method instead of an explicit for loop:

var students = classes.map(function(c) {
  var student = Object.assign({}, c.student);
  student.teacher = c.teacher;
  return student;
});

Upvotes: 2

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