Reproduce the problem and explain the reasons:
The label with the div v-if: level === 2, level initial value is -1, mounted only after completion of the execution of a function assigned to the level, the value of level it may be true; while rendering the chart on in the next line of an assignment statement, echarts probably can not find dom node. Because when the condition is false, v-if not rendered conditional block, only when the condition is true, it began to render conditional block.
solve:
The v-if into a v-show, because no matter how the conditions of the true value, v-show elements always be rendered.
Do not render echarts false when the condition.
If you can, consider make initial conditional expression is true.
v-if If the condition is false at the time of the initial rendering, rendering is not conditional block until the condition becomes true, it will begin to render conditional block.