send a request to server before submitting form

my requirement is as follows:-

I have javascript code for submitting for like:-

function submitForm(){
// task performing before submitting form
document.forms[0].submit();
}

before submitting form I want to send a request to server for getting some data and don’t want to submit final request until I get response of previous request.

new requirement is as follows:-

function submitForm(){
// task performing before submitting form

>>

send an request to server here and don’t want execution of next statements utill I get response

>>

Final submission

document.forms[0].submit();
}

Please help, It’s urgent

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