[Vuejs]-Vue get $index in two levels of v-for

<table>
    <tr v-for="(hid, height) in chartHeight" track-by="hid">
        <td class="item" v-for="(wid, width) in chartWidth" track-by="wid">
            {{ hid }}, {{ wid }}
        </td>
    </tr>
</table>