FormData的submitter参数

简单来说

1. button可以携带value值，并且在点击button时候，form提交会带上button的value

<button name="foo" value="bar" type="submit">Submit</button>

2. button带值可以有多个

<form action="/test-form" method="post">
    <button name="_action" value="delete" type="submit">Delete</button>
    <button name="_action" value="disable" type="submit">Disable</button>
</form>

3. 直接 new FormdData 不会携带button的value

const formdata = new FormData(form);

4. 使用 submitter 参数，可以指定提交某个button的value

form.addEventListener("submit", function (event) {
    event.preventDefault();
    const formdata = new FormData(form, event.submitter);
});

具体可参考 The submitter parameter for FormData