JavaScript - Starting with the basics - Case Study: Word Play(palindrome, FileReader, split, map, filter, join, regular expressions)

Think Perl 6

開発環境

• macOS Sierra - Apple (OS)
• Emacs (Text Editor)
• JavaScript (プログラミング言語)
• Node.js, Safari(JavaScript エンジン)
• Learning JavaScript [邦訳](参考書籍)

Think Perl 6: How to Think Like a Computer Scientist (Laurent Rosenfeld(著)、Allen B. Downey(著)、Oreilly & Associates Inc)の Part 1(Starting with the basics)、Chapter 8(Case Study: Word Play)の Exercise 8-7、8-8、8-9.を JavaScript で取り組んでみる。

Exercise 8-7、8-8、8-9.

words.txt

コード(Emacs)

HTML5

<pre id="output0"></pre>
<input id="file0" type="file">
<br>
<button id="run0">run</button>
<button id="clear0">clear</button>

<script src="sample7.js"></script>

JavaScript

let btn0 = document.querySelector('#run0'),
    btn1 = document.querySelector('#clear0'),
    pre0 = document.querySelector('#output0'),
    input_file0 = document.querySelector('#file0'),
    p = (x) => pre0.textContent += x + '\n',
    range = (start, end, step=1) => {
        let result = [];

        for (let i = start; i < end; i += 1) {
            result.push(i);
        }
        return result;
    };

let isPalindrome = (word) => word === word.split('').reverse().join('');

let output = () => {
    let file = input_file0.files[0],
        reader = new FileReader();

    reader.onload = () => {
        let words = reader.result
            .split('\n')
            .map((word) => word.trim())
            .filter((word) => word !== '');

        p('7.');
        p(
            words.filter((word) => /(.)\1(.)\2(.)\3/.test(word))
                .join('\n')
        );

        p('8.');
        p(
            range(100000, 1000000)
                .filter((n) =>
                        isPalindrome(`${n}`.substring(2)) &&
                        isPalindrome(`${n + 1}`.substring(1)) &&
                        isPalindrome(`${n + 2}`.substring(1, 5)) &&
                        isPalindrome(`${n + 3}`))
                .join('\n')
        );

        p('9.');
        let age1 = 20,
            age2 = 50;

        range(age1, age2 + 1)
            .forEach((diff) => {
                let count = 0;
                range(0, 100 - diff + 1)
                    .forEach((i) => {
                        let mum = i + diff;
                        if (`${i}` === `${mum}`.split('').reverse().join('')) {
                            p(`ME: ${i}, MUM: ${mum}`);
                            count += 1;
                        }
                    });
                if (count > 0) {
                    p(`${count}: ${diff}`);
                }
            })
    };
    reader.readAsText(file);
};

btn0.onclick = output;
btn1.onclick = () => pre0.textContent = '';

output();