LeetCode 2000. Reverse Prefix of Word

/**
 * @param {string} word
 * @param {character} ch
 * @return {string}
 */
var reversePrefix = function (word, ch) {
    if (word.length < 1 || word.length > 250) {
        return ""
    }

    const index = word.indexOf(ch)

    if (index === -1) {
        return word
    } else {
        const revertStr = word.substring(0, index + 1)
        const lastStr = word.substring(index + 1)
        let newString = ""
        for (let i = revertStr.length - 1; i >= 0; i--) {
            newString += revertStr[i]
        }

        return `${newString}${lastStr}`
    }

};