```ts
export function longWord(sentence: string): string {
    if (sentence === "") return "";
    
    const words = sentence.split(/\s+/);
    if (words.length === 0) return "";
    
    let longestWord = words[0];
    for (const word of words) {
        if (word.length > longestWord.length || (word.length === longestWord.length && words.indexOf(word) < words.indexOf(longestWord))) {
            longestWord = word;
        }
    }
    
    return longestWord;
}
```