Validate Phone

var n;
var p;
var p1;
var sayi=0;
function ValidatePhone(fi){

var p=fi.value

if(p.length==3){
var pp=p;
var d4=p.indexOf('(')
var d5=p.indexOf(')')
if(d4==-1){
pp="("+pp;
}
if(d5==-1){
pp=pp+")";
}


fi.value=pp;
}

if(p.length>3){
var d1=p.indexOf('(')
var d2=p.indexOf(')')
if (d2==-1){
var l30=p.length;
var p30=p.substring(0,4);
p30=p30+")"
var p31=p.substring(4,l30);
pp=p30+p31;
fi.value=pp;

}
}
if(p.length>5){
var p11=p.substring(d1+1,d2);
if(p11.length>3){
var p12=p11;
l12=p12.length;
var l15=p.length
var p13=p11.substring(0,3);
var p14=p11.substring(3,l12);
p15=p.substring(d2+1,l15);

pp="("+p13+")"+p14+p15;

fi.value=pp;
}
l16=p.length;
p16=p.substring(d2+1,l16);
l17=p16.length;
if(l17>3&&p16.indexOf('-')==-1){
p17=p.substring(d2+1,d2+4);
p18=p.substring(d2+4,l16);
p19=p.substring(0,d2+1);
pp=p19+p17+"-"+p18;

fi.value=pp;
}
}

}


<İnput type="text" name="Telefon" size="35" class="inputfont" onkeydown="ValidatePhone(this)" maxlength="13" onKeypress="if (event.keyCode <> 57) event.returnValue = false;">

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