How to choose between `window.URL.createObjectURL()` and `window.webkitURL.createObjectURL()` based on browser

Question

From the Firefox developer website, I know that Firefox uses

objectURL = window.URL.createObjectURL(file);

to get url of file type, but in

Answer 1

Simple one liner:

var createObjectURL = (window.URL || window.webkitURL || {}).createObjectURL || function(){};