Setting a JSON value in a JavaScript Variable

Hi fórum...

I have a SAP UI5 XML View and a JSON Model, the view show the value in a text component:

<Text xmlns="sap.m" id="iduser" text="{userapi>/displayName}"></text>

That´s correct, and show the value in the App,,,, "But i want to setting the value in a JavaScript Variable.... for use it  in another thing.. i don´t know how to do it...  "

I call the JsonModel from the index.html... and i want the variable there.

!!