Historical Transparency MapBox workshop example

<!DOCTYPE html>
//Lines 4 - 51 Set up the map and the style.
//Lines 53 - 60 Insert the map and the Layer Opacity info box. 
//Lines 63 -73 Pull in your specific map data from MapBox. Line 67 is your you would insert the style from your Mapbox account.
<html>
<head>
    <meta charset='utf-8' />
  
    <title>Adjust a layer's opacity</title>
    <meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
    <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.49.0/mapbox-gl.js'></script>
    <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.49.0/mapbox-gl.css' rel='stylesheet' />
    <style>
        body { margin:0; padding:0; }
        #map { position:absolute; top:0; bottom:0; width:100%; }
    </style>
</head>
<body>

.map-overlay .map-overlay-inner {
    background-color: #fff;
    box-shadow:0 1px 2px rgba(0, 0, 0, 0.20);
    border-radius: 3px;
    padding: 10px;
    margin-bottom: 10px;
}

.map-overlay label {
    display: block;
    margin: 0 0 10px;
}

.map-overlay input {
    background-color: transparent;
    display: inline-block;
    width: 100%;
    position: relative;
    margin: 0;
    cursor: ew-resize;
}
</style>

<div class='map-overlay top'>
    <div class='map-overlay-inner'>
        <label>Layer opacity: <span id='slider-value'>100%</span></label>
        <input id='slider' type='range' min='0' max='100' step='0' value='100' />
    </div>
</div>

var slider = document.getElementById('slider');
var sliderValue = document.getElementById('slider-value');

map.on('load', function() {

map.addLayer({
        "id": "HOLC1939",
        "source": {
            "type": "raster",
            "url": "mapbox://andy-rutkowski.a0p1p0hr"
        },
        "type": "raster"
    });

slider.addEventListener('input', function(e) {
        // Adjust the layers opacity. layer here is arbitrary - this could
        // be another layer name found in your style or a custom layer
        // added on the fly using `addSource`.
        map.setPaintProperty('HOLC1939', 'raster-opacity', parseInt(e.target.value, 10) / 100);

// Value indicator
        sliderValue.textContent = e.target.value + '%';
    });
});
</script>

</body>
</html>

https://api.tiles.mapbox.com/mapbox-gl-js/v0.49.0/mapbox-gl.js