vue使用百度地图报错BMap is not defined问题及解决

<script type="text/javascript" src="http://api.map.baidu.com/api?v=2.0&ak=你的密钥"></script

externals: {
    "BMap": "BMap"
  },

<script src="https://api.map.baidu.com/api?v=2.0&ak=此处填写申请的百度地图AK"></script>

<template>
  <div id="map"></div>
</template>
<script>
let BMap = {};
let map = {};
export default {
  methods: {
    createMap() {
      BMap = window.BMap;
      map = new BMap.Map("map");
      map.centerAndZoom("成都", 11);
    },
  },
  created() {
    this.$nextTick(() => {
      this.createMap();
    });
  },
};
</script>
 
<style scoped>
#map {
  width: 100%;
  height: 1000px;
}
</style>