reverse-prefix-of-word_0326.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>reverse-prefix-of-word</title>
</head>
<body>
    
</body>
<script>
const word = "abcdefd";
const ch = "d";

console.log(reversePrefix(word, ch));
/**
 * @param {string} word
 * @param {character} ch
 * @return {string}
 */
function reversePrefix(word, ch) {
    if(word.indexOf(ch) == -1) return word;
    
    const index = word.indexOf(ch) + 1;
    const reverseStr = word.slice(0, index).split("").reverse().join("");
    const lastStr = word.slice(index, word.length);
    
    return reverseStr + lastStr
};
</script>
</html>