Add pre-defined country code

I'm working on adding a pre-defined country code to the input form so that it is automatically set when the user begins filling out the form.
<input class="form-control rounded-start" id="cellNumber" name="cellNumber" dmx-bind:value="value?'WHATEVER'+(value.replace(/\D/g, '')):null" placeholder="+371" data-rule-digits=""> - works just perfectly, but when I'm replacing with needed cuntry code <input class="form-control rounded-start" id="cellNumber" name="cellNumber" dmx-bind:value="value?'+371'+(value.replace(/\D/g, '')):null" placeholder="+371" data-rule-digits=""> I see this:

Also tried to be "smart" and tried this combination value?('+371').toString()+(value.replace(/\D/g, '')):null - still no luck

Anyone?

Come up with this solution - value.replace('+371','')?(value.startsWith('+371')?value.replace(/[^\d+]/g,''):'+371'+value.replace(/\D/g,'')):null