livienyin / lexvlex Goto Github PK

These are questions @livienyin had about #3.

[4:40 PM] livien: are "L._______" leaflet functions?

[4:44 PM] livien: what's the difference between including "var" and not including "var" in "Fix variable definition error in style function"?

[5:02 PM] livien: For "function onEachFeature(feature, layer) {
layer.on('click', function(e) {
map.fitBounds(e.target.getBounds());
});
layer.bindPopup(popup(feature));
};" --> Where does the "e" come from and what type of an object is it?

1. L.__________: I'm not sure how to define this well, but I'll give it a try. (@eeeschwartz should jump in and explain it better!) Leaflet.js is an API that has a bunch of classes in it. One class is a "map": L.map makes a map object. The map has a series of options (which you see in the { } here) and a series of methods you can run on it. L.geoJson and L.tileLayer are also Leaflet objects: you can read more about them in the API doc here.
2. This change has to do with variable scope. By defining the tractColor in the style function with var, it means that tractColor only has meaning inside of that function. Anything inside of the function knows what it is, but tractColor has no meaning outside of that function. If we decided we needed to access that variable elsewhere in the code, we could leave off the var, making it a "global variable" that can be accessed anywhere.
3. The layer.on('click') method is an event handler. It says, "When someone clicks on the map, do this function." The Leaflet map class can have quite a few events. The e here represents the event itself -- in this case, click. The callback function that takes e as a parameter is creating an event handler for the click -- it says when you click, fit the bounds of the map to whatever was clicked on. e.target.getBounds() says take the click, find out what was clicked on (the target), and get the bounds of that object. That bounding box is then passed as an argument to the map.fitBounds() method, and the map zooms to that bounding box.

[ ] Kill pan
[ ] Kill zoom
[ ] Darken on selected
[ ] Hover with title