How to Pass a Parameter from URL to Query in UI Page ServiceNow jelly Scripting?

Retrieve Parameter Value from within a UI page:

<g:evaluate var="sysparm_id">

var sysparm_name = RP.getParameterValue("sysparm_name"); -> here you specify the name of your parameter !

sysparm_name;

</g:evaluate>

Use parameter in your script:

<g:evaluate var="jvar_user" object="true" jelly="true">

var gr = new GlideRecord("sys_user");

gr.get("name",jelly.sysparm_name);

gr;

</g:evaluate>