我们通过在声明组件之前添加以下行解决了这个问题。
declare var L: any;

myclass.component.ts

import { Component, OnInit } from '@angular/core';
...

// Leaflet and Leaflet Routing Machine have been installed with npm
import 'leaflet-routing-machine';
import 'leaflet-easybutton';

// Add this line to remove typescript errors
declare var L: any;

@Component({
  ...
})
export class MyClass extends OnInit {
  ...

  constructor(...) {
    ...
  }

  ngOnInit() {

    ...

    // The example snippet is now working
    L.Routing.control({
      waypoints: [
        L.latLng(57.74, 11.94),
        L.latLng(57.6792, 11.949)
      ]
    }).addTo(myMap);

    ...

  }

  ...

}

正如本文所提到的，typescript似乎会导致向Leaflet的全局L对象添加属性的问题，但在我们的例子中，声明any类型的L足以使其工作。

不确定Leaflet Routing Machine插件是否直接导出自身。
通常，它至少应该具有附加到L全局名称空间的副作用。
在调用require('leaflet-routing-machine')之后，您是否尝试过使用L.routing.control示例化控件？（注意启动L）

好的。怎么用！
1)npm i leaflet-routing-machine https://www.npmjs.com/package/leaflet-routing-machine
2)npm i leaflet-easybutton https://www.npmjs.com/package/leaflet-easybutton
3)工作页面中的导入模块：

import leaflet from 'leaflet'; 
import 'leaflet-routing-machine'; 
import 'leaflet-easybutton';

4)声明L declare var L:any;
添加代码内容

var maptt = leaflet.map('mapId2');
leaflet.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', { 
    attribution: '©suwitbb' 
}).addTo(maptt);

leaflet.Routing.control({ 
    waypoints: [ 
        leaflet.latLng(57.74, 11.94), 
        leaflet.latLng(57.6792, 11.949) 
    ], routeWhileDragging: true 
}).addTo(maptt);

6)添加标签查看html

在Ionic 4中，尝试一下。
1)npm i传单。
2)npm i leaflet-routing-machine.
3)在“index.html”中导入js和css。

<!-- Leaflet CDN JS and Css-->
<link rel="stylesheet" href="https://unpkg.com/leaflet@1.4.0/dist/leaflet.css" integrity="sha512-puBpdR0798OZvTTbP4A8Ix/l+A4dHDD0DGqYW6RQ+9jxkRFclaxxQb/SJAWZfWAkuyeQUytO7+7N4QKrDh+drA==" crossorigin="" />
<script src="https://unpkg.com/leaflet@1.4.0/dist/leaflet.js" integrity="sha512-QVftwZFqvtRNi0ZyCtsznlKSWOStnDORoefr1enyq5mVL4tmKB3S/EnC3rRJcxCPavG10IcrVGSmPh6Qw5lwrg==" crossorigin=""></script>

<!-- Leaflet Machine. path: 'node_modules/leaflet-routing-machine/dist/leaflet-routing-machine.js' the same to css-->
<link rel="stylesheet" href="./assets/css/leaflet-routing-machine.css">
<script src="./assets/js/leaflet-routing-machine.js"></script>

4)在your_component.ts中

import Leaflet from 'leaflet';
import 'leaflet-routing-machine';

// Add this line to remove typescript errors
declare var L: any;

export class FullScreenMapPage implements OnInit { 
  // mapa
  mapa: any;

  ionViewDidEnter() {
    this.drawMap();
  }

drawMap(): void {
    // marcador del mapa
    const markerGroup = Leaflet.featureGroup();
    const marker = Leaflet.marker([lat, lng]);

    this.mapa = Leaflet.map('map').setView([lat, lng], 11);

    Leaflet.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
    attribution: '© Open Street Map',
    zoom: 8,
    maxZoom: 18,
    minZoom: 4,
    minResolution: 4891.96981025128,
    maxResolution: 39135.75848201024,
    doubleClickZoom: true,
    center: [lat, lng]
    }).addTo(this.mapa);

    Leaflet.Routing.control({
      waypoints: [
        Leaflet.latLng(PointA_lat, PointB_lng),
        Leaflet.latLng(PointB_lat, PointB_lng)
      ], routeWhileDragging: true
    }).addTo(this.mapa);

  }

}

一个更好的选择是为leaflet-routing-machine安装类型，而不是“将L声明为any”。

npm install --save-dev @types/leaflet-routing-machine

这样所有的方法和属性都将被识别。这对我来说效果好多了！

const instance = L.Routing.control({
    waypoints: [
        startCoords,
        endCoords
    ],
    lineOptions: {
        styles: [{ color: "rgba(14, 162, 246, 1)", weight: 6 }],
        missingRouteTolerance: 0,
        extendToWaypoints: false
    },
    show: false,
    addWaypoints: false,
    routeWhileDragging: false,
    fitSelectedRoutes: false,
    showAlternatives: false,
});