What is missing part in using Leaflet

I am new to JavaScript and wish to use Leaflet map.

I installed npm, and use npm to install Leaflet and typescript.

So what else I should do? The following code is done in VSCode.

<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Shape</title>
    
    <link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/leaflet.css" />
    <style>
        #map {
            width: 100%;
            height: 100vh;
        }
    </style>
</head>
<body>
    <div id = "base_map"></div> 
</body>
</html>
<script src="https://unpkg.com/[email protected]/dist/leaflet.js"></script>

<script >
    var map = L.map('map').setView([51.505, -0.09], 13);

    var osm = L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
    attribution: '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors'});
    osm.addTo(map);

</script>

The result is a blank white page.

Solution

Map div width set to 100% of div#base_map?

Try putting those css attributes on #base_map instead:

<style>
    #base_map {
        width: 100%;
        height: 100vh;
    }
</style>