Intersection of two Strings JS

itersection.ts

    private itersection(textOne: string, textTwo: string): string {
        let textOneIndex: number = 0;
        let textTwoIndex: number = 0;
        let matchedText: string = '';
        
        textOne = textOne.toLowerCase();
        textTwo = textTwo.toLowerCase();

        while (textOneIndex < textOne.length && textTwoIndex < textTwo.length) {
            if (textOne[textOneIndex] < textTwo[textTwoIndex]) {
                textOneIndex++;
            } else if (textTwo[textTwoIndex] < textOne[textOneIndex]) {
                textTwoIndex++;
            } else {
                matchedText = `${matchedText}${textTwo[textTwoIndex++]}`
                textOneIndex++;
            }
        }

        return matchedText;
    }