在字符串中查找文本，将其存储在数组中并显示它

I am trying to find a strings in a string content and pushing the found content letter by letter in an array and display all the found content in html. But it seems like something wrong with the for loop (do not run it crashes). What would be the best practice to achieve something like this without using regex. Code is located below.I am trying to find a strings in a string conte