问从输入字段验证onchange文件名(纯javascript)

EN

<form>
<input type="file" onchange="return validateSize()" id="uploadFile" accept="image/*">
<button type="submit">Send</button>
</form>

function validateSize() {
const file = document.querySelector('#uploadFile');
const file_name = file.value;
const extension = file_name.split('.').pop().toLowerCase();
const size = file.files[0].size;
const allowedFormats = ["jpg", "jpeg"];
if (((size/1024)/1024) > 4) {
    // works perfect
    alert("Please optimize your image to maximum 4MB!");
    file.value = "";
    return false;
}
else if (!(allowedFormats.indexOf(extension) > -1)) {
    // works perfect
    alert("Please save your image in JPG format!");
    file.value = "";
    return false;
}
else if ((/^[a-z0-9\s\,\.\-\_]{5,50}\.(?:jpg|jpeg)$/i.test(file_name)) ==  false) {
    // this IS NOT working
    alert("Filename can have only letters (a-z), numbers, spaces, dots, '-' and '_'!");
    file.value = "";
    return false;
}
}

/^[a-z0-9\s\,\.\-\_]{5,50}\.(?:jpg|jpeg)$/i