How to download geojson data and read it to R - r

Question

# From http://leafletjs.com/examples/choropleth/us-states.js
states <- geojsonio::geojson_read("json/us-states.geojson", what = "sp")
bins <- c(0, 10, 20, 50, 100, 200, 500, 1000, Inf)
pal <- colorBin("YlOrRd", domain = states$density, bins = bins)
labels <- sprintf(
"<strong>%s</strong><br/>%g people / mi<sup>2</sup>",
states$name, states$density
) %>% lapply(htmltools::HTML)
leaflet(states) %>%
setView(-96, 37.8, 4) %>%
addProviderTiles("MapBox", options = providerTileOptions(
id = "mapbox.light",
accessToken = Sys.getenv('MAPBOX_ACCESS_TOKEN'))) %>%
addPolygons(
fillColor = ~pal(density),
weight = 2,
opacity = 1,
color = "white",
dashArray = "3",
fillOpacity = 0.7,
highlight = highlightOptions(
weight = 5,
color = "#666",
dashArray = "",
fillOpacity = 0.7,
bringToFront = TRUE),
label = labels,
labelOptions = labelOptions(
style = list("font-weight" = "normal", padding = "3px 8px"),
textsize = "15px",
direction = "auto")) %>%
addLegend(pal = pal, values = ~density, opacity = 0.7, title = NULL,
position = "bottomright")
The above code is copied from https://rstudio.github.io/leaflet/choropleths.html.
I am trying to reproduce the output. However, I got stuck in the first step - downloading the geojson file. I used the link shown in the first line, and save it as a text file and then rename it as a geojson file. But I failed to read that file. Obviously something wrong with file download or loading to R, but I have no idea where it is.
Can someone give any instructions? I have never deal with geojson data before. I just need help with the first two lines of codes, and I can handle all the others by myself.

Answer 1

The download file has a javascript assignment at the head. Removing it seems to fix the issue ,
library(geojson)
library(geojsonio)
url <- "http://leafletjs.com/examples/choropleth/us-states.js"
# read as text file
doc <- readLines(url)
# remove the javascript assignment at the front
doc2 <- gsub("var statesData = ", "", doc)
# write out as a temp file and read
write(doc2, file = "tempgeo.json")
states <- geojson_read("tempgeo.json", what = "sp")