https://daq00.triumf.ca/MidasWiki/index.php/Custom_Page#modb

says that

If the ODB path does not point to an individual value but to a subdirectory, the 
whole subdirectory is mapped to this.value as a JavaSctipt object such as

<div class="modb" data-odb-path="/Runinfo" onchange="func(this.value)">

<script>function func(value) { console.log(value["run number"]); }</script>


In fact, it seems to return the JSON string of said object, so you'd have to write

console.log(JSON.parse(value)["run number"])