How to return a value when using execute_script in capybara?

Question

I have a really simple line in a test that calls execute script like this:

puts page.execute_script(\"return somefunction();\").to_i.inspect

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Answer 1

The Poltergeist driver is designed to return nil for execute_script:

def execute_script(script)
  browser.execute(script)
  nil
end

Poltergeist will only return a value if you use the evaluate_script:

def evaluate_script(script)
  browser.evaluate(script)
end

Capybara has corresponding methods for each - ie Session#execute_script and Session#evaluate_script. Your code should work if you switch to using evaluate_script (and as @AndreyBotalov points out, you also need to remove the return):

puts page.evaluate_script("somefunction();").to_i.inspect