post request to json file

Question

I'm trying to make a post request to json file using JQuery, and for the server I'm using npm package live-server. But I got this error in chrome console:

POST http://127.0.0.1:8080/user.json 405 (Method Not Allowed)

here's my index.js:

$('#new').submit(function (e) {
        e.preventDefault()
        const fname = $('.fname').val();
        const lname = $('.lname').val();
        const url = $(this).attr('action');
    
        $.ajax({
            method: 'post',
            url: 'user.json',
            data: { fname, lname },
            dataType: 'json'
        }).done(function (data) {
            console.log(data);

        });
    })

my index.html:

<form id="new" action="user.json">
            <label for="">fname</label>
            <input class="fname" type="text" placeholder="fName">
            <label for="">lname</label>
            <input class="lname" type="text" placeholder="lName">
            <input type="submit" value="submit">
 </form>

the json file I wanna make the request to, user.json:

[
    {
        "fname": "fola",
        "lname": "abdallah"
    },
    {
        "fname": "maha",
        "lname": "abdallah"
    },
    {
        "fname": "Moe",
        "lname": "abdallah"
    }
]

when I make get request it works very well, so what's the issue exactly I could be missing the obvious