<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-js -->
let arr = ['1','2','0','3','0',undefined,'0',undefined,'3','',''];
// map everything to Number (undefined becomes NaN)
// filter all valid numbers
arr = arr.map(Number).filter(e => !isNaN(e))
console.log(arr);
<!-- end snippet -->
<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-js -->
var myJSONObject = {"ircEvent": "PRIVMSG", "method": "newURI", "regex": "^http://.*"};
delete myJSONObject.regex;
console.log ( myJSONObject.regex); // logs: undefined
<!-- end snippet -->
This works in Firefox and Internet Explorer, and I think it works in all others.
