If object does not have key, add it.
Hindi dapat direktang i-install ang script na ito. Ito ay isang library para sa iba pang mga script na isasama sa meta directive. // @require https://update.greasyfork.org/scripts/427473/937466/object_setDefault.js
Added method setDefault to object prototype.
function setDefault (key, value)
If object does not have key, add it with value value
key (string, required)
key to check
value (any, optional, default = undefined)
value for key if it's not present