Javascript changes const variables also [duplicate]

Question

let courses = [ {id:1, name : "Femin"}, {id:2, name : "Darsh"}, {id:3, name : "Smit"}, ]; let enteredId = 2; const course = courses.find(c => c.id === enteredId); course.name = "Darsh Bhimani"; console.log(course); console.log(courses);

So this is the code I've been working with. I have been working with Java and C,C++ for the past 5-6 years and started with Javascript a week back. (For node.js).

Now what I am finding confusing here are two things:

The variable course is a constant, still its value can be changed. How ?
The course is fetched from the array courses, but still on changing course, when I log courses, I see that the value of the array has also changed. How is that possible?

In this case it does not matter if the value changes, but when I don't want the array to change, what can I do?

const in JavaScript only means the variable cannot be re-assigned, the properties of objects can still change. — skyline3000
– skyline3000, Commented Jun 29, 2019 at 18:55

Nina Scholz · Accepted Answer · 2019-06-29 18:56:12Z

You get with find an object reference and to break this, you could get a shallow copy of the object with Object.assign. This approach works undefined as well, but returns in that case an empty object.

let courses = [ {id:1, name : "Femin"}, {id:2, name : "Darsh"}, {id:3, name : "Smit"}, ]; let enteredId = 2; const course = Object.assign({}, courses.find(c => c.id === enteredId)); course.name = "Darsh Bhimani"; console.log(course); console.log(courses);

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