Any interactive web site has form input - a place where the users input different kind of information.
This data is passed to ASP script, or some other technology and if the data contains an error, there will be a delay before the information travels over the Internet to the server, is examined on the server, and then returns to the user along with an error message.
If the element complies than sufunction returns an empty string.
Otherwise it returns a message describing the error and highlight appropriate element with yellow.
If you run a validation of the users form input before the form is submitted, there will be no wait time and redundant load on the server.
If the required field is blank, we return the error string to the main function.I'll include the code below, but you can run/fork it on Codepen.HTML One thing I know could be improved is where I repeat basically the same code twice to validate the characters in each section.IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.Often, email validation code for web applications checks only for the position of @ and period characters, also assuming the @ character will be in the front of period. Did you know you can use a Java Script Regular Expressions method to check email addresses?