Edit in JSFiddle

// resize map
const mapdiv = document.getElementById('mapid');
var margin;
if (document.all) {
  margin = parseInt(document.body.currentStyle.marginTop, 10) + parseInt(document.body.currentStyle.marginBottom, 10);
} else {
  margin = parseInt(document.defaultView.getComputedStyle(document.body, '').getPropertyValue('margin-top')) + parseInt(document.defaultView.getComputedStyle(document.body, '').getPropertyValue('margin-bottom'));
}
mapdiv.style.height = (window.innerHeight - margin) + 'px';

/////
var map = L.map('mapid').setView([22.29227, 114.20847], 8);

var apikey = 'f4d3e21d4fc14954a1d5930d4dde3809' //landsd.azure-api.net starter key
var apikey = '584b2fa686f14ba283874318b3b8d6b0' //api.hkmapservice.gov.hk starter key

L.tileLayer('https://api.hkmapservice.gov.hk/osm/xyz/worldimagery/WGS84/tile/{z}/{x}/{y}.png?key=' + apikey, {
attribution: "<a href='https://api.portal.hkmapservice.gov.hk/disclaimer' target='_blank'>&copy; Imagery from NASA/Lands Department <img src='https://api.hkmapservice.gov.hk/mapapi/landsdlogo.jpg' style='width:25px;height:25px'/></a>",
    maxZoom: 19,
}).addTo(map);

L.tileLayer('https://api.hkmapservice.gov.hk/osm/xyz/sclabel-en/WGS84/tile/{z}/{x}/{y}.png?key=' + apikey, {
//attribution: "<a href='https://api.portal.hkmapservice.gov.hk/disclaimer' target='_blank'>&copy; Imagery from NASA/Lands Department</a>",
    maxZoom: 19,
}).addTo(map);
#mapid {
  height:100%;
  width:100%;
}
.leaflet-container .leaflet-control-attribution {
  background: transparent;
}
<div id="mapid"></div>

External resources loaded into this fiddle: