How to write data to json file from form using Ajax?

Question

JavaScript

I am making a tool, so to speak for myself, will be used on OpenServer.
I need to enter data into a json file through a form. It looks like this

[
    ["11.09.2018",222],
    ["12.09.2018",392],
    ["13.09.2018",485],
    ["14.09.2018",449],
    ["15.09.2018",449],
    ["16.09.2018",449],
    ["17.09.2018",449],
    ["18.09.2018",449]
]

There are 2 fields in the form: date and number.
How to implement all this via ajax so that new records are added in this format and at the end of the file?

Answer 1

Given what you said about openServer, I suspect that you will have a backend in php.
1. Create a form

<form action="#" id="test">
    <input type="date" name="date">
    <input type="number" name="num">
    <input type="submit">
</form>

2. Send it via ajax

$(function(){

    $('#test').on('submit', function(){

        let data = $(this).serialize();

        $.ajax({
            method: 'POST',
            url: 'test.php',
            data: data
        }).done(function( msg ){
            console.log( msg );
        });

        return false;
    });
});

3. Add data to json file

$file = file_get_contents('data.json');
$list = json_decode($file,TRUE); 
unset($file);
$list[] = [ $_POST['date'], $_POST['num'] ];
file_put_contents('data.json',json_encode($list));