#2000 - Reverse Prefix of Word

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Problem Description

Given a 0-indexed string word and a character ch, reverse the segment of word that starts at index 0 and ends at the index of the first occurrence of ch (inclusive).

If the character ch does not exist in word, do nothing.

For example, if word = "abcdefd" and ch = "d", then you should reverse the segment that starts at 0 and ends at 3 (inclusive). The resulting string will be "dcbaefd".

Solution

/**
 * @param {string} word
 * @param {character} ch
 * @return {string}
 */
var reversePrefix = function(word, ch) {
  const index = word.indexOf(ch) + 1;
  return word.slice(0, index).split('').reverse().join('') + word.slice(index);
};