JSFiddle - React, Tailwind, and code Playground

JavaScript

var books = [
    {
    title: "Inheritance: Inheritance Cycle, Book 4",
    author: "Christopher Paolini",
    },
{
    title: "The Sense of an Ending",
    author: "Julian Barnes"},
{
    title: "Snuff Discworld Novel 39",
    author: "Sir Terry Pratchett",
    }
]
search = prompt("Title?");

function count(pattern)
{
    var results = [];
    var matches = null;
    pattern = new RegExp(pattern, "g")
    
    for (i = 0; i < books.length; i++) {
        results[i] = 0;
        matches = books[i].title.toLowerCase().match(pattern);
        if(matches != null) {
            results[i] = matches.length;
        }
    }
    return results
}

alert(count(search))