Can't call method of OpenLayers object: 'getSource is not a function'

Question

I'm using OpenLayers 7.5.2 to create a simple map with one vector layer having two points. This works. I want to then access the layer object in the map and get to the point features to update their text attributes. However, I get "Uncaught TypeError: l.getSource is not a function" in the browser when I attempt to access the style objects, starting with getSource():

    let lyrs = map_obj.getAllLayers(); //works
    for (let l in lyrs) {
        source = l.getSource(); //doesn't work
        features = source.getFeaturesCollection(); //??
        for (let f in features) {
            alert('a feature');                 
        }
    }

Per the ol documentation, the getSource method belongs to the layer object. This seems straight-forward so I'm at a loss. I'm new to OpenLayers.

Here's my test page for reference.

Can you give me any pointers?

Answer 1

In in my code sample, above, the syntax of l.getSource() is incorrect. Here's an updated code sample with corrected syntax.

let lyrs = map_obj.getAllLayers(); 
for (let l in lyrs) {
    source = lyrs[l].getSource();           
    let features = source.getFeaturesCollection();          
    features.forEach( function (feat, index) {  
        alert(index);                           
    });         
}