replace_word function for javascript developers. See original function here: https://gist.github.com/Songbird0/978bf046b37a2969c51495336c7c29ef

replace_word_jsstyle.js

function replace_word(initial_string, word, newWord) {
    var index = initial_string.indexOf(word);
    if (index !== -1) {
        var first_part = '';
        var mid_part = '';
        var second_part = '';
        if (index === 0) {
            first_part = newWord;
            second_part = sliceAt(initial_string, word);
            return "" + first_part + second_part;
        }
        if (index === (initial_string.length - 1)) {
            first_part = sliceAt(initial_string, word);
            second_part = newWord;
            return "" + first_part + second_part;
        }
        if (index > 0 && index < (initial_string.length - 1)) {
            var word_length = word.length;
            first_part = initial_string.substring(0, index);
            mid_part = newWord;
            second_part = initial_string.substring(index + word_length);
            return "" + first_part + mid_part + second_part;
        }
    }
    return null;
}