使用Jquery Keyup函数将变量从一个输入字段传递到另一个输入字段

I am trying to autopopulate an input field (location-name) with the value entered in another field (location-address). I have looked online everywhere and managed to make the JS snippet work on a straightforward example, but for some reason this is not working with the following php code.

Just to clarify, I would like the value entered in "location-address to be passed to "location-name".

<script>
    $('#location-address')
        .keyup(function() {
            var value = $(this).val();
            $('#location-name').text(value);
        })
        .keyup();
</script>

<tr class="em-location-data-name">
    <th style="padding-top: 14px;">
        <?php _e ( 'Event unique identifier:', 'dbem' )?>
    </th>
    <td>
        <input id="location-name" type="text" name="location_name" />
    </td>

</tr>
<tr class="em-location-data-address">
    <th style="padding-top: 14px;">
        <?php _e ( 'Address:', 'dbem' )?>&nbsp;</th>
    <td>
        <input id="location-address" type="text" name="location_address" value="<?php echo esc_attr($EM_Location->location_address, ENT_QUOTES); ; ?>" />
    </td>
</tr>

You need to wrap your jQuery code in $(document).ready(); so that jQuery binds all HTML elements.

Corrected code:

<script>
$(document).ready(function(){
$('#location-address').keyup(function() {
    var value = $(this).val();
    $('#location-name').val( value );
  });
}).keyup();
</script>

Firstly your code needs to be placed in a document.ready handler. Secondly, you need to use val() not text() to set the value of an input field.

$(function() {
    $('#location-address').keyup(function() {
        var value = $(this).val();
        $('#location-name').val(value);
    }).keyup();
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table>
  <tr class="em-location-data-name">
    <th style="padding-top: 14px;">
      <?php _e ( 'Event unique identifier:', 'dbem' )?>
    </th>
    <td>
      <input id="location-name" type="text" name="location_name" />
    </td>
  </tr>

  <tr class="em-location-data-address">
    <th style="padding-top: 14px;">
      <? php _e( 'Address:', 'dbem') ?>&nbsp;
    </th>
    <td>
      <input id="location-address" type="text" name="location_address" value="<?php echo esc_attr($EM_Location->location_address, ENT_QUOTES); ; ?>" />
    </td>
  </tr>
</table>

</div>

Use this

<script>
$(document).ready(function(){
$('#location-address').keyup(function() {
    var value = $(this).val();
    $('#location-name').val( value );
  });
});
</script>