python-selenium: execute_script vs execute_async

Question

is not very clear to me the difference between execute_script and execute_async_script in selenium.

given this example in python-selenium, into a pytest function:

driver.get(url)

js = '''
var video = document.getElementById("myVideo");

video.onplaying=function() {
  return "play";
};
'''

video_play = driver.execute_script(js)
assert video_play == "play"

the result is:

E       AssertionError: assert None == 'play'

what am i missing? should i use execute_async and an async/await function in js? could you point me at some examples?

Tarun Lalwani · Accepted Answer · 2017-09-03 09:37:32Z

5

You need to use async script for this.

driver.get(url)

js = '''
var callback = arguments[arguments.length - 1];
var video = document.getElementById("myVideo");

video.onplaying=function() {
  callback ("play");
};

setTimeout(function(){
  callback("notplayed");
}, 2000);
'''

video_play = driver.execute_async_script(js)
assert video_play == "play"

What above does is that it waits for 2 secs max for the playback to happen if it doesn't then notplayed is returned.

Do remember that the call will not return until the script has finished. So don't think that you can execute some other code after the async script. Until the callback or async timeout, the code will be stuck at execute_async_script

answered Sep 3, 2017 at 9:37

Tarun Lalwani

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