导入Lit-HTML时，“无法在模块外部使用import语句”

Question

我正在尝试导入Lit-HTML，但出现错误：Uncaught SyntaxError: Cannot use import statement outside a module

我使用npm安装此库（版本：6.14.6）

我的index.js（我只有一个javascript文件）：

import {render, html, svg} from 'lit-html';

const tasksElement = document.querySelector("#tasks");

const titleInput = document.querySelector("#title");
const descriptionInput = document.querySelector("#description");
const priorityInput = document.querySelector("#priority");
const dateInput = document.querySelector("#date");
const timeInput = document.querySelector("#time");
const submit = document.querySelector("#submit");

我的package.json：

    {
  "name": "timemanagement",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "dependencies": {
    "lit-html": "^1.3.0"
  },
  "devDependencies": {},
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC"
}

我得到的错误：index.js:1 Uncaught SyntaxError: Cannot use import statement outside a module