\
**Category:** Help\
**Created:** [January 9, 2020, 4:12am UTC](https://talk.observablehq.com/t/dry-leaflet-layers-the-html-template-literal/2727 "2020-01-09T04:12:13Z")\
**Posts on this page:** 4\
**Page:** 1
**Author:**  [@aaronkyle](https://talk.observablehq.com/u/aaronkyle)\
**Post date:** [January 9, 2020, 4:12am UTC](https://talk.observablehq.com/t/dry-leaflet-layers-the-html-template-literal/2727/1 "2020-01-09T04:12:13Z")
### DRY Leaflet Layers
I am working on a map that will have many, many layers:
> **[Nepal Layers](https://observablehq.com/d/9aef18a2b092b886)**
>
> An Observable notebook by Aaron Kyle Dennis.
… When adding in each layer, I use this pattern:
```auto
var barhabise_access_road_line = $.getJSON("https://geospatial-analysis.s3.amazonaws.com/NEP/50059-002/barhabise-access-road_line.geojson",function(data){
L.geoJson(data).addTo(map);
});
```
… but I wonder, do I really need to do this for each layer? Or can I instead reference a list of URLs (such as in a CSV file) and thereby only use one function to call in several layers?
I realize that loading in several layers with one function (if possible) would limit my ability to independently style / color each layer, but I expect the trade-off might be that I can define a generic style for a group of similar layers (all blue markers for heritage sites, etc).
### HTML Template Literal
Somewhat related: I am trying to defined a content string in a separate named cell, and then referencing that cell by its name in my function:
For example, this would be the content of the named cell:
```auto
barhabise_access_road = html`https://geospatial-analysis.s3.amazonaws.com/NEP/50059-002/barhabise-access-road_line.geojson`
```
which I would then reference in the map cell, like so:
```auto
var barhabise_access_road_line = $.getJSON(barhabise_access_road,function(data){
L.geoJson(data).addTo(map);
});
```
It looks like it should work, as the map cell recognizes the named value as being valid (the name turns blue), but the layer won’t appear.
Am I making a simple syntax error? Should I escape something? Or is there another reason this approach doesn’t work?
I note that when I call just the cell by name elsewhere after defining it, I don’t see the string, but instead I am returned an HTML text element. I expect this has something to do with why its not working, but I don’t know how to work around it. Probably I am just being silly…
Thanks in advance for your help and insights!
---
**Author:**  [@j-f1](https://talk.observablehq.com/u/j-f1)\
**Post date:** [January 9, 2020, 12:37pm UTC](https://talk.observablehq.com/t/dry-leaflet-layers-the-html-template-literal/2727/2 "2020-01-09T12:37:50Z")
Something like this should work:
```auto
Promise.all(["https://geospatial-analysis.s3.amazonaws.com/NEP/50059-002/barhabise-access-road_line.geojson", "another URL"].map(url => d3.json(url).then(data => L.geoJson(data).addTo(map)))
```
I’m not sure what you’re trying to do with the `html` template tag so I can’t help you with that.
---
**Author:**  [@aaronkyle](https://talk.observablehq.com/u/aaronkyle)\
**Post date:** [January 9, 2020, 1:00pm UTC](https://talk.observablehq.com/t/dry-leaflet-layers-the-html-template-literal/2727/3 "2020-01-09T13:00:50Z")
Thanks Jed!
As for the template tag - I was just looking at further ways to abstract and shorten the code used to generate each layer. Specifically, I wanted to list out each URL as a separate cell, and just refer to the cell name in the function.
---
**Author:**  [@aaronkyle](https://talk.observablehq.com/u/aaronkyle)\
**Post date:** [January 9, 2020, 1:44pm UTC](https://talk.observablehq.com/t/dry-leaflet-layers-the-html-template-literal/2727/4 "2020-01-09T13:44:34Z")
OK, I was being foolish.
I confused myself about the HTML rendering after first trying to enter just a string in a named cell, like this:
```auto
barhabise_access_road = `https://geospatial-analysis.s3.amazonaws.com/NEP/50059-002/barhabise-access-road_line.geojson`
```
… The returned string contained the ticks, which _appeared_ to go away after I used the HTML tag. But this was pure folly.
When I instead used double quotes to around my URL, it worked correctly in my function:
```auto
barhabise_access_road = "https://geospatial-analysis.s3.amazonaws.com/NEP/50059-002/barhabise-access-road_line.geojson"
```
Thanks for bearing with me and for the help!