Javascript (jQuery) - Weird undefined variable

Question

Here is my jQuery function

function addEntryDatabase(data){
    var entryId;
    $.ajax({
        url: "model/script_ajout.php",  
        async: false,
        type: "POST",
        dataType: 'html',
        data: data
        success: function()
        {

        },
        error: function(){
            console.log('An error occurred while adding adata to the database.');
        }
    });
    return entryId;
}

Here is my code

/**
 * Creating user in the database
 */
var user_id = addEntryDatabase(data);
console.log(user_id);

Here is the console of my web browser (everything is fine, I get my entryId value)

But my console.log of user_id give me 'undefinned'. I can not explain why.

Did somebody know why ?

You declare entryId without a value (var entryId;) and then you return it (return entryId;). At no point are you assigning a value to it. The default value is undefined. — Felix Kling
– Felix Kling, Commented Sep 27, 2021 at 9:46

Jai248 · Accepted Answer · 2021-09-27 09:49:29Z

1

After success, you need to change your entryId with the response you get in which you will have the id which you want to log.

function addEntryDatabase(data){
    var entryId;
    $.ajax({
        url: "model/script_ajout.php",  
        async: false,
        type: "POST",
        dataType: 'html',
        data: data
        success: function()
        {
          entryId= response.data.id ///change your entryId;
        },
        error: function(){
            console.log('An error occurred while adding adata to the database.');
        }
    });
    return entryId;
}```

answered Sep 27, 2021 at 9:49

Jai248

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4 Comments

Beko Over a year ago

So simple.. thank you !

Jai248 Over a year ago

welcome.Please accept the solution :)

phuzi Over a year ago

If you try to access the result before the AJAX request has completed (or if it errors) the value will still be undefined.

Jai248 Over a year ago

yeah, it will only give undefined if there is an error.

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