Rvest wont return data

Question

I have been trying to scrape the following table:

Answer 1

Your problem was that your request delivered you a html site, not a json response. Thus, parsing it as a json failed with the error you saw.
(I can't tell you exactly whether it was because you missed out on the accept_json() or whether the URL you used was a bit off.).

Either way, reverse engineering the essentials of the API request behind the table you linked, you'd have to put something like this together:

require(httr)
require(dplyr)
library(purrr)

first_req <- GET("https://www.barchart.com")
xsrf_token <- cookies(first_req) %>% filter(name == 'XSRF-TOKEN') %>% pull(value) %>% URLdecode()

req <- GET(
    "https://www.barchart.com/proxies/core-api/v1/quotes/get",
    query = list(
      lists = "stocks.optionable.by_sector.all.us",
      fields = "symbol,symbolName,lastPrice,priceChange,percentChange,highPrice,lowPrice,volume,tradeTime,symbolCode,symbolType,hasOptions",
      orderBy = "symbol",
      orderDir = "asc",
      meta = "field.shortName,field.type,field.description",
      hasOptions = TRUE,
      #page = 1,
      #limit = 100,
      raw = 1
    ),
    content_type_json(),
    accept_json(),
    add_headers(
      "x-xsrf-token" = xsrf_token,
      "referrer" = "https://www.barchart.com/options/stocks-by-sector?page=1"
    )
  )

table_data <- req %>%
  content() %>%
  .$data %>%
  map_dfr(unlist)

This will get you the full list of 4258 items and coerce it into a tibble for convenience :)