How Do I Resume Processing an Array?

I have this “book” array where numbers identify chpt., paragraph and verse of included text element:

book = [[1,1,1, “Once upon a time I was born to a diabetic mom”],
[1,1,2, “They called me Manny the fatty”],
[1,1,3, “That is because I was blubbery and round”],
...
[34,18,17, “The end”]]

The processing starts from the array's beginning. I parse out each sentence for its words, and each word for its letters.

At some point, inside of a word, while examining a letter, I need to halt, to do some tangential search downstream from here.

Then I need to get back to this same letter I was investigating, and continue processing where I left off.

for (x = 0; book[x][0] < 35 || book[x] != undefined; x++){

verseWords = book[x][3].split(" ");
wordCount = verseWords.length;
for (y=0; y < wordCount; y++) {

letterCount = verseWords[y].length;
for (z=0; z < letterCount; z++) {

if (verseWords[y][z] == ....​

How do I get back to where I was (to the word and letter I was at) and resume processing?

Suppose I want to check if the letter "X" exists 200 letters from where I am, how do I get back to where I was, to continue?

I would need a function call. Take the code above; Suppose after the line that reads: if (verseWords[y][z] == .... I want to do this "by-the-way" search for letter X;
I haven't any idea how to code the function or its parameter requirements, because I'm 3 levels deep in FOR loops.

 

Can you redo it over?
I feel something like this could be done a lot easier with object literal or JSON object than with the array.

If you go that deep for the nested for loop, I can tell that something is terribly terribly wrong.