JavaScript: Loop through a Google Spreadsheet

JavaScript: Loop through a Google Spreadsheet

In our post Coding marker maps with Leaflet.js we filled a map visualization with information given directly in the code, but we also learned how to loop through data in a JSON file to create markers and pop-ups. This time, we will loop through an public Google Spreadsheet. We will do this with the same example map as in the previous post. But this little trick will not only help you with building marker maps but can come in handy for any JavaScript application you need to automate the handling of your data.

So let’s start right away with setting up a data table with Google Spreadsheets.

JavaScript: Coding marker maps with Leaflet.js

JavaScript: Coding marker maps with Leaflet.js

Showing locations on a map can be pretty cool to provide some context for your story or to give your reader an overview of where the story takes place. A good way to build a simple, yet responsive and professional looking map is to use the JavaScript library Leaflet.

In an earlier post, “Your first choropleth map“, we used Leaflet as well, but coded the map using the Leaflet R package, which works like a wrapper to translate the more common Leaflet functions into R syntax. It’s very useful if you’re more used to R syntax and don’t want to learn JavaScript anytime soon. But using the original JS library and coding the map with JavaScript will give us way more freedom when customizing the map, which is why we’ll try it that way today.

As an example, let’s start with a map of the locations of some data journalism newsrooms in the German speaking area. As always you can find all the code of this tutorial on our GitHub page.

This is what the finished map will look like:

Your first interactive choropleth map with R

Your first interactive choropleth map with R

When it comes to data journalism, visualizing your data isn’t what it’s all about. Getting and cleaning your data, analyzing and verifying your findings is way more important.

Still, an interactive eye-catcher holding interesting information will definitely not hurt your data story. Plus, you can use graphics for a visual analysis, too.

Here, we’ll show you how to build a choropleth map, where your data is visualized as colored polygon areas like countries and states.
We will code a multilayer map on Dortmunds students as an example. You’ll be able to switch between layered data from different years. The popups hold additional information on Dortmunds districts.