Vue 3: How to update component props value correctly using composition api?

Question

I have like this component:

<template>
  <div>
    <p>Current coords: <strong>{{ coords }}</strong></p>
    <button type="button" @click="updateCoords">
  </div>
</template>
<script>
export default {
  props: {
    coords: {
      type: Array,
      required: true
    }
  },
  setup(props) {
    const updateCoords = () => {
      props.coords = [38.561785, -121.449756]
      // props.coords.value = [38.561785, -121.449756]
    }
    return { updateCoords }
  },
}
</script>

I tried update prop coords value with updateCoords method but I get error message:

Uncaught TypeError: Cannot set properties of undefined (setting 'coords')

How I can correctly update props value in my case?

Answer 1

Props are readonly:
https://v3.vuejs.org/guide/component-props.html#one-way-data-flow

If you want to have two way binding for props, you'll need to implement the v-model pattern:
https://v3-migration.vuejs.org/breaking-changes/v-model.html#_3-x-syntax

<template>
  <div>
    <p>Current coords: <strong>{{ coords }}</strong></p>
    <button type="button" @click="updateCoords">
  </div>
</template>
<script>
export default {
  props: {
    modelValue: {
      type: Array,
      required: true
    }
  },
  emits: ['update:modelValue'],
  setup(props, {emit}) {
    const updateCoords = () => {
        emit('update:modelValue', [38.561785, -121.449756])
    }
    return { updateCoords }
  },
}
</script>