如何在Ruby中读取JavaScript变量并转为JSON以获取GBP汇率

Alright, let's get this sorted. You've already fetched the raw JavaScript string using Net::HTTP—great start! Now we just need to parse that JS into a Ruby hash (which works just like JSON for easy indexing) so you can grab the GBP rate quickly.

Here are two reliable approaches to do this:

Method 1: Use Regular Expressions + JSON Parsing (No Extra Gems) #

This method extracts the Currency.rates object from the JS string, converts it to valid JSON, then parses it into a Ruby hash.

require 'net/http'
require 'uri'
require 'json'

# Fetch the JS file content
uri = URI('http://cdn.shopify.com/s/javascripts/currencies.js')
response = Net::HTTP.get(uri)

# Match the Currency.rates object using regex
rates_match = response.match(/Currency\.rates = ({.*?});/)

if rates_match
  # Convert JS object syntax to valid JSON (add quotes around keys)
  js_rates_str = rates_match[1].gsub(/(\w+):/, '"\1":')
  # Parse into a Ruby hash
  rates_hash = JSON.parse(js_rates_str)
  # Grab the GBP rate
  gbp_rate = rates_hash['GBP']

  puts "GBP exchange rate: #{gbp_rate}"
else
  puts "Oops—couldn't find the Currency.rates object in the response. Double-check the JS file structure!"
end

Notes on this method: #

• The regex targets the exact pattern Currency.rates = { ... }; to pull out the rate data.
• We use gsub to add double quotes around unquoted keys (since JSON requires quoted keys, but JS allows unquoted ones).
• This works if the JS file's structure stays consistent, but might break if Shopify changes how they format the Currency.rates variable.

Method 2: Use ExecJS (More Robust, Handles Edge Cases) #

If you want a solution that's less prone to breaking from JS syntax changes, use ExecJS to run the JavaScript directly and extract the Currency.rates object. This requires the execjs gem (which relies on a JS runtime like Node.js—most Ruby environments have this pre-installed).

First install the gem if you haven't:

gem install execjs

Then use this code:

require 'net/http'
require 'uri'
require 'execjs'

# Fetch the JS file content
uri = URI('http://cdn.shopify.com/s/javascripts/currencies.js')
response = Net::HTTP.get(uri)

# Compile and execute the JS, then extract the rates object
js_context = ExecJS.compile(response)
rates_hash = js_context.eval('Currency.rates')

# Get the GBP rate directly from the hash
gbp_rate = rates_hash['GBP']

puts "GBP exchange rate: #{gbp_rate}"

Notes on this method: #

• ExecJS runs the actual JavaScript code, so it handles any valid JS syntax (like trailing commas, unquoted keys, etc.) that might trip up regex/JSON parsing.
• It's more reliable long-term, even if Shopify tweaks their JS formatting.

Either method will let you access the GBP rate via rates_hash['GBP'] once you've parsed the data. Pick the one that fits your environment and needs!

内容的提问来源于stack exchange，提问作者Asad Shakil