import { Line as LineChart } from 'vue-chartjs'
import { Chart as ChartJS, Tooltip, CategoryScale, LinearScale, PointElement, LineElement, Legend } from 'chart.js'
import zoomPlugin from 'chartjs-plugin-zoom'
ChartJS.register(CategoryScale, Legend, Tooltip, LinearScale, PointElement, LineElement, zoomPlugin)
<script>
export default {
 components: {
 LineChart
 },
 methods: {
 test () {
 this.$refs.lineChart.chart // null
 this.$refs.lineChart.chartInstance // null too
 }
 }
}
</script>
<template>
 <LineChart
 id="my-chart-id"
 ref="lineChart"
 />
</template>