Vue Datepicker wont show default date onrender

Question

I have a Vue app which is loading another component that implements a range date field using vue-datepicker. I want it to have a default range of last 7 days when it first renders.

However, I can't set the data to it on render, even though I am passing it to the component via :value attribute.

My date picker component code:

<template>
    <div>
        <Datepicker
            v-model="selectedDates"
            type="range"            
            :value="[startDate, endDate]"
            @change="onDateChange"
            range            
            :enable-time-picker="false"
            format="MMM dd"
        />
    </div>
</template>

<script>
import Datepicker from "@vuepic/vue-datepicker"

export default {
    components: {
        Datepicker,
    },
    data() {
        return {
            selectedDates: [this.startDate, this.endDate],
            startDate: new Date(new Date().setDate(new Date().getDate() - 7)),
            endDate: new Date(),
        }
    },
    methods: {
        onDateChange() {
            this.$emit("date-change", this.selectedDates)
        },
    },
}
</script>

There are no errors in browser console, either.

Answer 1

You can't define data props based on other data props directly. You can define the value for your prop directly by using:

<template>
    <div>
        <Datepicker range
            v-model="selectedDates"
            @change="onDateChange"         
            :enable-time-picker="false"
            format="MMM dd" />
    </div>
</template>

<script>
    import Datepicker from "@vuepic/vue-datepicker"

    export default {
        components: {
            Datepicker,
        },
        data() {
            return {
                selectedDates: [new Date(new Date().setDate(new Date().getDate() - 7)), new Date()],
            }
        },
        methods: {
            onDateChange() {
                this.$emit("date-change", this.selectedDates)
            },
        },
    }
</script>

Note that we now don't reference other properties when defining selectedDates.

Or you can use computed properties, which is cleaner in my opinion:

<template>
    <div>
        <Datepicker range
            v-model="selectedDates"
            @change="onDateChange"         
            :enable-time-picker="false"
            format="MMM dd" />
    </div>
</template>

<script>
    import Datepicker from "@vuepic/vue-datepicker"

    export default {
        components: {
            Datepicker,
        },
        computed: {
            startDate() {
                return new Date(new Date().setDate(new Date().getDate() - 7));
            },
            endDate() {
                return new Date();
            },
            selectedDates() {
                return [this.startDate, this.endDate]
            }
        }
        methods: {
            onDateChange() {
                this.$emit("date-change", this.selectedDates)
            },
        },
    }
</script>

Also note that you bind to both v-model and :value. I would suggest only binding to v-model.