How do I guarantee that everything inside a onsubmit callback will get run before the form is submitted?

How do I guarantee that everything inside a onsubmit callback will get run
before the form is submitted?

References

Reference NO 1

http://stackoverflow.com/questions/13644205/how-do-i-guarantee-that-everything-inside-a-onsubmit-callback-will-get-run-befor

Reference NO 2

http://stackoverflow.com/questions/9930149/how-to-use-ajax-callback-to-determine-when-to-submit-form

Reference NO 3

https://www.braintreepayments.com/docs/javascript/encryption/usage

Reference NO 4

http://callbackhell.com/

Reference NO 5

http://community.servicenow.com/forum/16012

Reference NO 6

http://facebook.github.io/react/docs/tutorial.html

Reference NO 7

http://www.drlongghost.com/validanguage/documentation_advanced

Reference NO 8

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