This Ajax Code doesn't work in WordPress

I’m trying to implement an ajax contact form. In a static site it works well but in WordPress in spite of that i can sent mails. The contact form stops showing the message “sending mail”. I don’t know what’s the problem.

Here you can see the contact form working well on a static page: http://www.elated.com/res/File/articles/development/javascript/jquery/slick-ajax-contact-form-jquery-php/

This is the Javascript code where ajax is:

var messageDelay = 2000;  // How long to display status messages (in milliseconds)

// Init the form once the document is ready
$( init );

// Initialize the form

function init() {

  // Hide the form initially.
  // Make submitForm() the form's submit handler.
  // Position the form so it sits in the centre of the browser window.
  $('#contactForm').hide().submit( submitForm ).addClass( 'positioned' );

  // When the "Send us an email" link is clicked:
  // 1. Fade the content out
  // 2. Display the form
  // 3. Move focus to the first field
  // 4. Prevent the link being followed

  $('a[href="#contactForm"]').click( function() {
    $('#content').fadeTo( 'slow', .2 );
    $('#contactForm').fadeIn( 'slow', function() {
      $('#senderName').focus();
    } )

    return false;
  } );

  // When the "Cancel" button is clicked, close the form
  $('#cancel').click( function() {
    $('#contactForm').fadeOut();
    $('#content').fadeTo( 'slow', 1 );
  } );  

  // When the "Escape" key is pressed, close the form
  $('#contactForm').keydown( function( event ) {
    if ( event.which == 27 ) {
      $('#contactForm').fadeOut();
      $('#content').fadeTo( 'slow', 1 );
    }
  } );

}

// Submit the form via Ajax

function submitForm() {
  var contactForm = $(this);

  // Are all the fields filled in?

  if ( !$('#senderName').val() || !$('#senderEmail').val() || !$('#message').val() ) {

    // No; display a warning message and return to the form
    $('#incompleteMessage').fadeIn().delay(messageDelay).fadeOut();
    contactForm.fadeOut().delay(messageDelay).fadeIn();

  } else {

    // Yes; submit the form to the PHP script via Ajax

    $('#sendingMessage').fadeIn();
    contactForm.fadeOut();

    $.ajax( {
      url: contactForm.attr( 'action' ) + "?ajax=true",
      type: contactForm.attr( 'method' ),
      data: contactForm.serialize(),
      success: submitFinished
    } );
  }

  // Prevent the default form submission occurring
  return false;
}

// Handle the Ajax response

function submitFinished( response ) {
  response = $.trim( response );
  $('#sendingMessage').fadeOut();

  if ( response == "success" ) {

    // Form submitted successfully:
    // 1. Display the success message
    // 2. Clear the form fields
    // 3. Fade the content back in

    $('#successMessage').fadeIn().delay(messageDelay).fadeOut();
    $('#senderName').val( "" );
    $('#senderEmail').val( "" );
    $('#message').val( "" );

    $('#content').delay(messageDelay+500).fadeTo( 'slow', 1 );

  } else {

    // Form submission failed: Display the failure message,
    // then redisplay the form
    $('#failureMessage').fadeIn().delay(messageDelay).fadeOut();
    $('#contactForm').delay(messageDelay+500).fadeIn();
  }
}// JavaScript Document

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