Regular expression to allow + at the start and digits

I have this code.
How I can change it to allow only numbers and + at the start.

$(document).on("input", ".numeric>input , .numeric", function() {
    this.value = this.value.replace(/[^0-9\.]/g,'');
});

Let me know and many thanks!

>Solution :

You can easily add the + as the first digit, as i understand you are trying to match a phone number, your code must be as the following :

$(document).on("input", ".numeric>input , .numeric", function() {
    this.value = this.value.replace(/[+0-9\.]/g,'');
});

here is a beautiful online tool where you can build them easily, you do not have to memorise everything :

RegEx