JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/amplifyjs/1.1.0/amplify.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery-mockjax/1.5.1/jquery.mockjax.js"></script>
<pre id="output"></pre>

JavaScript

var $output = $( "#output" );

$.mockjax(function ( settings ) {
    if ( typeof settings.data === "string" ) {
        $output.append( "<code>[New] Content: " + settings.data + "</code><br>" );
    } else {
        $output.append( "<code>[Old] Form Data: " + JSON.stringify( settings.data, null, "\t" ) + "</code><br>" );
    }
    return {};
});

amplify.request.define('update-customer', 'ajax', {
    url : 'rest/customer/{b}',
    dataType: 'json',
    type : 'PUT',
    contentType : 'application/json; charset=utf-8',
    dataMap: function ( data ) {
         return JSON.stringify( data );   
    }
});

amplify.request.define('update-customer-old', 'ajax', {
    url : 'rest/customer/{a}',
    dataType: 'json',
    type : 'PUT',
    contentType : 'application/json; charset=utf-8'
});


amplify.request( "update-customer-old", { a: "aaa", b: "bbb", c: "ccc" });
amplify.request( "update-customer", { a: "aaa", b: "bbb", c: "ccc" });