Warning message for repetitive keys in template loop

Question

Warning message for repetitive keys in template loop

<template v-for="errors in validationErrors">
    <li v-for="(error, errIdx) in errors" :key="errIdx">{{ error }}</li>
</template>

An issue arises with the above code:

The system detects duplicate keys: '0'. This might lead to an update error.

By eliminating index from the inner loop and assigning error as the key, the warning disappears. However, this solution seems incorrect.

Is there a way to avoid this warning when using templates?

javascript vue.js vuejs2 v-for

Answer 1

Answer №1

Try using this alternative approach:

<template v-for="(errors, outerIndex) in validationErrors">
    <li v-for="(error, index) in errors" :key="outerIndex + '-' + index">
        {{ error }}
    </li>
</template>

Explanation

If the outer loop does not provide unique information, the inner loop key will result in duplicate values. For example, with two outer loops containing 3 items each, you might see:

<li key="0">...</li>
<li key="1">...</li>
<li key="2">...</li>
<li key="0">...</li>
<li key="1">...</li>
<li key="2">...</li>

By incorporating an outerIndex as well, you can ensure that each inner element remains unique:

<li key="0-0">...</li>
<li key="0-1">...</li>
<li key="0-2">...</li>
<li key="1-0">...</li>
<li key="1-1">...</li>
<li key="1-2">...</li>

Answer 2

Try using this alternative approach:

<template v-for="(errors, outerIndex) in validationErrors">
    <li v-for="(error, index) in errors" :key="outerIndex + '-' + index">
        {{ error }}
    </li>
</template>

Explanation

If the outer loop does not provide unique information, the inner loop key will result in duplicate values. For example, with two outer loops containing 3 items each, you might see:

<li key="0">...</li>
<li key="1">...</li>
<li key="2">...</li>
<li key="0">...</li>
<li key="1">...</li>
<li key="2">...</li>

By incorporating an outerIndex as well, you can ensure that each inner element remains unique:

<li key="0-0">...</li>
<li key="0-1">...</li>
<li key="0-2">...</li>
<li key="1-0">...</li>
<li key="1-1">...</li>
<li key="1-2">...</li>

Warning message for repetitive keys in template loop

Answer №1

Explanation

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