VueJS computed properties data binding issue

Question

https://jsfiddle.net/rohan0793/h7gn8qdv/

So I was trying to implement a simple todo list with computed properties like in the above fiddle. There are 3 lists. All Tasks. Completed Tasks. Incomplete Tasks. The problem is that if I click on the checkbox of an incomplete task in Incomplete List, or a complete task in Completed List, the task below it gets toggled too. I am not sure why this behaviour. Is it because the event is propagating somehow? I tried @click.stop on the checkboxes too but with no luck

tony19 · Accepted Answer · 2022-07-15 21:46:28Z

3

The issue here is you are not using any key attribute in the loop. The key special attribute is primarily used as a hint for Vue's virtual DOM algorithm to identify VNodes when diffing the new list of nodes against the old list.

Without keys, Vue uses an algorithm that minimizes element movement and tries to patch/reuse elements of the same type in-place as much as possible. Thus you are getting the below behaviour:

if I click on the checkbox of an incomplete task in Incomplete List, or a complete task in Completed List, the task below it gets toggled too.

So, to resolve this you simply need to bind key to each loop like:

<li v-for="task in incompleteTasks" :key="task.id">
   <input type="checkbox" v-model=task.completed>{{ task.description }}
</li>

With keys, it will reorder elements based on the order change of keys, and elements with keys that are no longer present will always be removed/destroyed.

Working Fiddle

edited Jul 15, 2022 at 21:46

tony19

140k23 gold badges281 silver badges354 bronze badges

answered May 8, 2020 at 4:50

palaѕн

74.2k17 gold badges123 silver badges140 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Rohan Over a year ago

Ah, I added the ids in the array, and I thought I used them too. Stupid of me. Thanks for pointing this out.

Collectives™ on Stack Overflow

VueJS computed properties data binding issue

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related