CODEWITHSUNDEEP
javascriptarrays
Ferdi Louwerse
Ferdi Louwerse

Reputation: 99

Only change copy of array

I'm trying to duplicate some items of an array. I change some objects with new id's, the problem is that not only the new array is modified but also the original.

The code I use:

function cloneProductLine(oldGroupIndex) {
    // Create new instance of the product lines
    let items = [...productLines];
    let group = items.find((line, index) => index === parseFloat(oldGroupIndex));

    // Get product lines with same parent group Id
    items = items.filter((line) => line.parent_group_id === group.group_id);
    items.forEach((line) => line.parent_group_id = getNewGroupId());

    // Set new Id for group
    group.group_id = getNewGroupId();

    productLines = [...productLines, group, ...items];


    renderProductLine();
  }

What am I doing wrong?

Upvotes: 1

Views: 48

Answers (2)

Kiran Shinde
Kiran Shinde

Reputation: 5982

Or Simple way

let items = JSON.parse(JSON.stringify(productLines));

Upvotes: 1

Yury Tarabanko
Yury Tarabanko

Reputation: 45121

let items = [...productLines]; creates a shallow array copy. Means all items are the same though the array is new.

You need to create a deeper copy (create new items as well)

Assuming items are plain old objects you could do

let items = productLines.map(item => ({...item});

Upvotes: 1

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