vue cli4.0项目引入typescript的方法

npm install --save-dev typescript
npm install --save-dev @vue/cli-plugin-typescript

{
 "compilerOptions": {
 "target": "esnext",
 "module": "esnext",
 "strict": true,
 "importHelpers": true,
 "moduleResolution": "node",
 "experimentalDecorators": true,
 "esModuleInterop": true,
 "allowSyntheticDefaultImports": true,
 "sourceMap": true,
 "baseUrl": ".",
 "allowJs": false,
 "noEmit": true,
 "types": ["webpack-env"],
 "paths": {
  "@/*": ["src/*"]
 },
 "lib": ["esnext", "dom", "dom.iterable", "scripthost"]
 },
 "exclude": ["node_modules"]
}

declare module '*.vue' {
 import Vue from 'vue';
 export default Vue;
}

src/main.js => src/main.ts

src/main.js => src/main.ts

import { Vue, Component ,Watch} from 'vue-property-decorator';
@Component({
 components: { Loading }
})
export default class App extends Vue{
 old_back:object=null,
 transitionName:string = "slide-right";
 get ...mapState("base", ["loadingStatus"]);
 @Watch('$route')
 onChangeValue(to:object, from:object){
  // console.log('$route', to, from)
  const noBack = to.meta.noBack; // 监听路由变化时的状态为前进还是后退
  // 去终节点左，从终节点过来右
  if (to.meta.last) {
  this.transitionName = "slide-left";
  } else if (from.meta.last) {
  this.transitionName = "slide-right";
  } else if (from.meta.leaf) {
  // 从其它叶子页面过来的，往右
  this.transitionName = "slide-right";
  } else {
  if (noBack) {
   // 去到不需要返回的界面往右
   this.transitionName = "slide-right";
  } else {
   this.transitionName = "slide-left";
  }
  }
 }
 @Watch('loadingStatus')
 onChangeValue(newVal: string){
  if (newVal) {
  setTimeout(_ => {
   this.setLoading(false);
  }, 1500);
  }
 }
  // 弹出系统提示对话框
 showAlert(msg:string) {
  plus.nativeUI.alert(
  msg,
  function() {
   // console.log("User pressed!");
  },
  "报警详情",
  "确定"
  );
 }
}