timer function in javascript

Is there any method to capture the time taken from the alert message displayed till the users action to confirm the message using ja开发者_运维百科vascript

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Start a timer in Javascript when you display the message. Stop the timer when the user acknowledges the message. Use AJAX to submit the time to your PHP/CodeIgniter app.

Start a timer when you are going to ask a question on StackOverflow. Don't submit questions that take less than 5 seconds to write.