var cmDom = document.getElementsByClassName('CodeMirror');

// if multiple CodeMirror instances, for each one, the instance referece can be got from `CodeMirror` prop on the dom node
var editor1 = document.getElementsByClassName('CodeMirror')[0].CodeMirror;
// CodeMirror$1 object
// ...

var editor2 = document.getElementsByClassName('CodeMirror')[1].CodeMirror;
// CodeMirror$2 object
// ...