Range is a native type, it is the majority of browsers that you cannot create. I am not very familiar with Ace, but I assume that they use some kind of namespace so that you do something like new Ace.Range() .
Edit: It looks like they are using CommonJS, so you can import the method and alias as you like:
var Range = require('ace/range').Range, mine = new Range(0,0,10,0);
Prestaul
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