How do I fetch data from database through php to javascript variable?

Question

I have a jQuery UI datepicker. I want to send data to that function. I used .post function to fetch data from database as "data" through a PHP file. I am unable to access the data as the data returned to inside the .post function. I want it to the out side variable dat so that I can use it. Actually the data are the dates which are to be disable.

My code:

$(function () {
    var dat = "";
    var unavailableDates = ["10-5-2013", "14-5-2011", "15-5-2011"];
    var dt = "id=1";
    $.post("fetch.php", dt, function (data) {});
    dat = data;

    function enableFirday(date) {
        dmy = date.getDate() + "-" + (date.getMonth() + 1) + "-" + date.getFullYear();
        var day = date.getDay();
        return [((day == 6 || day == 5 || day == 3) && $.inArray(dmy, unavailableDates) < 0), ''];
    }
    $("#d").datepicker({
        beforeShowDay: enableFirday
    });
});

Inside the function there is a variable unavailableDates in the 3rd line. I want to fetch some date from my database and keep in that variable.

I thought I can use .post to fetch data from database so that I can use. But data are returned from PHP file and not copying to the variable dat. That are returned from PHP file can be used inside the .post function but not out side. How can I get the data to outside of the .post function. Please help me for this. It is very necessary to fetch data in my project.

You can use a hidden input field and store the values from Database in that. Use getElementbyId to fetch data to javascript variable. — Arup Rakshit
– Arup Rakshit, Commented Apr 18, 2013 at 20:20
Just so you are aware, stubbing out the callback like function(data) {} only scopes the data variable to that empty block you defined for the function and so the following assignment of dat = data will always evaluate to dat = undefined unless you set data somewhere globally (which is still not a good thing). @MarcB's answer says the root of your issue best I just wanted to point that out. — Brandon Buck
– Brandon Buck, Commented Apr 18, 2013 at 20:22

Derek 朕會功夫 · Accepted Answer · 2013-04-18 20:21:07Z

1

AJAX calls (your $.post()) ASYNCHRONOUS. Your JS code will run the .post() function, then continue onwards immediately. Unless you've got an insanely fast network link, it is virtually impossible for a response to come back from the AJAX call and populate the data variable.

That's why AJAX calls come with a callback handler, which JS will invoke when a response comes in from the server, so your code should be

var dat;
$.post(url, dt, function(data) {
    dat = data;
    enableFirday(); // or whatever your code should do once you get a response.
});

edited Apr 18, 2013 at 20:21

Derek 朕會功夫

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answered Apr 18, 2013 at 20:19

Marc B

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