When your chat button or contact form is integrated within your CMS you usually already know the e-mail address and name of your customer so you do not need to ask for it in a contact form.
You can prefill both the e-mail address, name or phone of the customer or any custom value by adding some special code to your widget code.
Since version 5.17 prefill methods logic has been changed and new method has been added.
More info here: https://support.liveagent.com/147815-Set-visitor-specific-values-with-javascript
And now a quick one-line solution examples...
Chat buttons
Regarding chat buttons, you are supposed to modify the original integration code
<script type="text/javascript">
(function(d, src, c) { var t=d.scripts[d.scripts.length - 1],s=d.createElement('script');s.id='la_x2s6df8d';s.async=true;s.src=src;s.onload=s.onreadystatechange=function(){var rs=this.readyState;if(rs&&(rs!='complete')&&(rs!='loaded')){return;}c(this);};t.parentElement.insertBefore(s,t.nextSibling);})(document,
'//URL_TO_LiveAgent/scripts/track.js',
function(e){ LiveAgent.createButton('16756da8', e); });
</script>
this way:
<script type="text/javascript">
(function(d, src, c) { var t=d.scripts[d.scripts.length - 1],s=d.createElement('script');s.id='la_x2s6df8d';s.async=true;s.src=src;s.onload=s.onreadystatechange=function(){var rs=this.readyState;if(rs&&(rs!='complete')&&(rs!='loaded')){return;}c(this);};t.parentElement.insertBefore(s,t.nextSibling);})(document,
'//URL_TO_LiveAgent/scripts/track.js',
function(e){
LiveAgent.setUserDetails('customer@email.com', 'First name', 'Last name');
LiveAgent.createButton('16756da8', e);
});
</script>
The row with bold letters
LiveAgent.setUserDetails('customer@email.com', 'First name', 'Last name');
was the one that was added to the original integration code.
Contact form
Regarding contact forms it is the same - if you compare the contact button and contact form code, then you will notice, that the only change is this:
LiveAgent.createButton() there is LiveAgent.createForm() so there is no difference between applying the above mentioned integration to a contact button code or to a contact form code.
Note: This integration is available for version 2.4 and higher.
Phone support
Since version 4.3.7.2 you can also prefill phone number in user details. This is the function form:
LiveAgent.setUserDetails(email, firstName, lastName, phone)
LiveAgent.setUserDetails(email, firstName, lastName, phone)