How to use external Js file in page and pass control value to Js file using JavaScript in ASP.Net

<script type="text/javascript">
function myFunction(id) {
   var txt = document.getElementById(id);
   txt.value = txt.value.replace(/\w\S*/g, function (txt) { return txt.charAt(0).toUpperCase() + txt.substr(1).toLowerCase(); });
}

function AddComma(text) {
    switch (text.value.length) {
       case 1:
           document.getElementById(text.id).value = "0.0" + text.value;
           break;
       default:
           var data = text.value.replace(".", "");
           var first = data.substring(0, (data.length - 2));
           var second = data.substring(data.length - 2);
           var temp = Math.abs(first) + "." + second;
           document.getElementById(text.id).value = temp;
     }
}
</script>

<div class="col-md-6">
     <div class="form-group">
         <label>Company Name<i class="text-red" style="font-size: large">*</i></label>
         <asp:TextBox ID="txt_company_name" runat="server" TabIndex="1" CssClass="form-control" onkeypress="return onlyAlphabets(event, this) && myFunction(this.id)" placeholder="Company Name" MaxLength="20"></asp:TextBox>
         <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="txt_company_name" ErrorMessage="Company Name Required" ForeColor="Red" TabIndex="1" SetFocusOnError="true" CssClass="pull-right" Font-Bold="true"></asp:RequiredFieldValidator>
     </div>
</div>

 The above javascript functions are used in many pages in my project so i wanted to minimise the code, I wrote a seperate javascript file and taking reference of that file as shown below.

<script src="Scripts/Functions.js" type="text/javascript"></script>

Problem is some functions are working like "onlyAlphabets(event, this)". you may see in textbox tag but these above functions aren't working...

Please help me...