function split(s) {
    var match;
    var result = [];
    while (Boolean(match = s.match(/([A-Z]+|[A-Z]?[a-z]+|[0-9]+|([^a-zA-Z0-9])+)$/))) {
        if (!match[2]) {
            //don't return non alphanumeric tokens
            result.unshift(match[1]);
        }
        s = s.substring(0, s.length - match[1].length);
    }
    return result;
}
 
console.log('P90X', split('P90X'));
console.log('TotallyCromulentWord', split('TotallyCromulentWord'));
console.log('TransAM', split('TransAM'));
console.log('URLConverter', split('URLConverter'));
console.log('Abc.DEF$012', split('Abc.DEF$012'));
 

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