How to update the data in normal array using mongodb

Question

I tried to update normal array data its sucessfully updated.but I have a doubt.I pass id in put url and get id to compare the array.its id is there its get data and stored another variable then that variable used to chanage the value.and its automatically change value in original array.How its possible any one can explain

app.js

const courses = [{id:1,product_name:"bourbon"},{id:2,product_name:"bourbon"}]  

router.put('/:id',(req,res) =>
{
    console.log("hello")
    console.log(req.params.id)
    for(let i=0;i<courses.length;i++)
    {
        if(courses[i].id === parseInt(req.params.id))
        {
            let course = courses[i]
            course.name = "hari"

            console.log(courses)
        }
    }

})

My put url
localhost:3000/woc/1

I got Output
[{id:1,product_name:"bourbon"},{id:2,product_name:"hari"}]

Ankit Bahuguna · Accepted Answer · 2019-06-18 10:21:54Z

1

You need to clone the original object. Just use let course = {...courses[i]} or let course = Object.assign({},courses[i]} instead of let course = courses[i].

Objects behave differently from primitive data types. The 'course' variable contains the reference to the element in the original array. So changing it is modifying the original object in the array.

edited Jun 18, 2019 at 10:21

answered Jun 18, 2019 at 10:16

Ankit Bahuguna

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