Add JS file reference in ts file in Angular

Hi,

I have this site that I am trying to add to my angular but having trouble adding js file.

https://www.youtube.com/watch?v=F8dnYNTncoU&t=533s

I tried the following:

I added the style sheet and links in the index.html in angular

I added the scripts in the json file and I added the js file in the assests folder

I am trying to reference the js file in the ts file but I don't know how since it is not starting as a function.

the js file:

// default map layer
let map = L.map('map', {
    layers: MQ.mapLayer(),
    center: [35.791188, -78.636755],
    zoom: 12
});
    

    function runDirection(start, end) {
        
        // recreating new map layer after removal
        map = L.map('map', {
            layers: MQ.mapLayer(),
            center: [35.791188, -78.636755],
            zoom: 12
        });
        
        var dir = MQ.routing.directions();

        dir.route({
            locations: [
                start,
                end
            ]
        });
    

        CustomRouteLayer = MQ.Routing.RouteLayer.extend({
            createStartMarker: (location) => {
                var custom_icon;
                var marker;

                custom_icon = L.icon({
                    iconUrl: 'img/red.png',
                    iconSize: [20, 29],
                    iconAnchor: [10, 29],
                    popupAnchor: [0, -29]
                });

                marker = L.marker(location.latLng, {icon: custom_icon}).addTo(map);

                return marker;
            },

            createEndMarker: (location) => {
                var custom_icon;
                var marker;

                custom_icon = L.icon({
                    iconUrl: 'img/blue.png',
                    iconSize: [20, 29],
                    iconAnchor: [10, 29],
                    popupAnchor: [0, -29]
                });

                marker = L.marker(location.latLng, {icon: custom_icon}).addTo(map);

                return marker;
            }
        });
        
        map.addLayer(new CustomRouteLayer({
            directions: dir,
            fitBounds: true
        })); 
    }


// function that runs when form submitted
function submitForm(event) {
    event.preventDefault();

    // delete current map layer
    map.remove();

    // getting form data
    start = document.getElementById("start").value;
    end = document.getElementById("destination").value;

    // run directions function
    runDirection(start, end);

    // reset form
    document.getElementById("form").reset();
}

// asign the form to form variable
const form = document.getElementById('form');

// call the submitForm() function when submitting the form
form.addEventListener('submit', submitForm);