ECharts For Vue  

import { createApp, h } from 'vue';
import echarts from 'echarts';
import { plugin } from 'echarts-for-vue';

const app = createApp({ /*...*/ });
app.use(plugin, { echarts, h });                        // use as a plugin

<template>
    <ECharts ref="chart" :option="option" />
</template>

<script>
    import echarts from 'echarts';
    import { h } from 'vue';
    import { createComponent } from 'echarts-for-vue';

    export default {
        components: {
            ECharts: createComponent({ echarts, h }),   // use as a component
        },
        data() {
            return {
                option: { /*...*/ },
            };
        },
        methods: {
            doSomething() {
                this.$refs.chart.inst.getWidth();       // call the method of ECharts instance
            },
        },
    }
</script>

import Vue from 'vue';
import echarts from 'echarts';
import { plugin } from 'echarts-for-vue';

Vue.use(plugin, { echarts });                           // use as a plugin

<template>
    <ECharts ref="chart" :option="option" />
</template>

<script>
    import echarts from 'echarts';
    import { createComponent } from 'echarts-for-vue';

    export default {
        components: {
            ECharts: createComponent({ echarts }),      // use as a component
        },
        data() {
            return {
                option: { /*...*/ },
            };
        },
        methods: {
            doSomething() {
                this.$refs.chart.inst.getWidth();       // call the method of ECharts instance
            },
        },
    }
</script>