assign function return value to some variable using javascript

Question

I have a js function   after doing some business logic  the javascript function should return some result to another variable Sample code below  var response     function doSomething             ajax           url  action php           type   POST           data  dataString          success  function  txtBack                 if txtBack  1                    status 1                            return status           Here i want to use like   response doSomething      I want to assign a return value  status    var response  But the result is  undefined

User · Answer

The only way to retrieve the correct value in your context is to run   ajax   function synchronously  what actually contradicts to main AJAX idea   There is the special configuration attribute async you should set to false  In that case the main scope which actually contains   ajax   function call is paused until the synchronous function is done  so  the return is called only after   ajax     function doSomething         var status   0        ajax           url   action php           type   POST           data  dataString          async  false          success  function  txtBack                if  txtBack    1                  status   1                         return status     var response   doSomething

User · Answer

The result is undefined since   ajax runs an asynchronous operation  Meaning that return status gets executed before the   ajax operation finishes with the request   You may use Promise to have a syntax which feels synchronous   function doSomething          return new Promise  resolve  reject    gt              ajax               url  action php               type   POST               data  dataString              success  function  txtBack                     if txtBack  1                        resolve 1                     else                       resolve 0                                                error  function  jqXHR  textStatus  errorThrown                    reject textStatus                                         You can call the promise like this  doSomething then function  result        console log result      catch function  error        console error error         or this   async      gt        try           let result   await doSomething            console log result         catch  error            console error error

User · Answer

You could simply return a value from the function   var response   0   function doSomething            some code     return 10    response   doSomething

User · Answer

AJAX requests are asynchronous  Your doSomething function is being exectued  the AJAX request is being made but it happens asynchronously  so the remainder of doSomething is executed and the value of status is undefined when it is returned   Effectively  your code works as follows   function doSomething someargums         return status     var response   doSomething      And then some time later  your AJAX request is completing  but it s already too late  You need to alter your code  and populate the  response  variable in the  success  callback of your AJAX request  You re going to have to delay using the response until the AJAX call has completed   Where you previously may have had  var response   doSomething     alert response     You should do   function doSomething             ajax              url  action php              type   POST              data  dataString             success  function  txtBack                 alert txtBack

User · Answer

Or just     var response    function         var a         calculate a     return a            In this case  the response variable receives the return value of the function  The function executes immediately     You can use this construct if you want to populate a variable with a value that needs to be calculated  Note that all calculation happens inside the anonymous function  so you don t pollute the global namespace

[jquery] assign function return value to some variable using javascript

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