Interview question: find numeral letter from a random string

jumble.js

const input = 'torzeonthowoereezero';

// idea here is, first check that every letter of numeral exist in the given string, 
// if it exist then remove the numeral letter from given string  and search for next numeral and so on

const numeral = {
    'zero' : 0,
    'one': 1,
    'two': 2,
    'three': 3,
    'four' : 4,
    'five': 5,
    'six': 6,
    'seven': 7,
    'eight': 8,
    'nine':9
};

const indexFound = (word, str) =>  str.indexOf(word) !== -1;

// check whether every letter exist on given string
const isExist = (word, str) => [...word].every((w) => indexFound(w, str));

//replace letter in string
const replaceLetter = (word, from) => word.replace(from, '');

const replacedWord = (word, str) => [...word].reduce(replaceLetter, str);

// check the occurrence of numeral letter in given string

const findOccurrence = ([sentence, collector], word) => {
	const exist = isExist(word, sentence);
	if(exist) {
	    collector.push((numeral[word])); // push respective number in separate array
		const replacedString  = replacedWord(word, sentence); // replace match word from input string
		return [replacedString, collector];
	} else {
        return [sentence, collector];
	}
}


const findJumbleWord = (input, next = []) => {
    // tricky part is we are sending array as initial value so that 
    // if there is multiple instance of the same literal then it will be done on next time calling of same method
    const [remains] = Object.keys(numeral).reduce(findOccurrence, [input, next]);
    if(remains.length > 2 ) { // as we know no numeral is less than 3 letter
        findJumbleWord(remains, next);
    }
    return next;
};

const result = findJumbleWord(input);

// now if we require to sort ascending and display as a number then

const resultSorted =  result.sort().join('');

console.log({result, resultSorted});