javascript - How to wait until the completion of asynchronous steps? -

javascript - How to wait until the completion of asynchronous steps? -

i have form need run number of validation actions before submitting. these actions involve asynchronous steps ajax calls.

how can tell form wait until validation actions have been completed before submitting?

my validation function looks (pseudo-code):

function presubmit() { // validate field 1 ajax({ ... onsuccess:... }); // validate field 2 ajax({ ... onsuccess:... }); // fields 3, 4, etc. }

my current issue form gets submitted before onsuccess callbacks completed.

i of course of study create ajax calls synchronous, trying avoid because of performance impact.

if you're using jquery, might want consider jquery.deferred or promise

you phone call each ajax request (or function contains request), when previous phone call finish (successfully or failed).

if utilize $.when can manage failed request .then callback. if utilize promises can create utilize .done .fail , .always callbacks in various scenarios.

$.when($.ajax("...."), $.ajax("....")) .then(...);

resources:

http://joseoncode.com/2011/09/26/a-walkthrough-jquery-deferred-and-promise/ http://api.jquery.com/jquery.when/ http://api.jquery.com/promise/

javascript forms validation submit