Store result of json request in a variable [duplicate]

I need to store a value of json response to use in another function.

I have this code:

const url_moodle = "https://xxxxx/xxxxx/app/appmoodlejson.php";var moodleEmail = function (email){  $.post( url_moodle, { "email":email, "postvar":"email" }, "json")    .done(function( data, textStatus, jqXHR ) {      if(data.data){       // console.log(data.data.id_mdl);       return data.data.id_mdl;      }    })    .fail(function( jqXHR, textStatus, errorThrown ) {      toastr.error('Error, contact support');      if ( console && console.log ) {        console.log( "Fail response: " +  textStatus);      }    });};var id_mdl = moodleEmail('someemail@emailsome.com');

If I go to browser console use console.log, data.data.id_mdl show correctly value, but if I use "return" to store value, code no show any error and no function.

Please helpe with any idea to resolve this.