JavaScript method to validate the text field, the text field should be mandatory

function Validate()
 {
			var txt_cold = document.getElementById("<%=txt_cold.ClientID%>");
            if (txt_cold.value.length <= 0)
             {
                alert("Permit Type Cold Work field cannot be blank!");
                document.getElementById("<%=txt_cold.ClientID%>").focus();
                return (false);
            }
            
}