JavaScript - Starting with the basics - Hashes(Finding Duplicates with a Hash(Object), Rotate Pairs)

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 10(Hashes)の Exercise: 10-3、10-4.を JavaScript で取り組んでみる。

Exercise: 10-3、10-4.

words.txt

コード(Emacs)

HTML5

<pre id="output0"></pre>
<input id="file0" type="file">

<button id="run0">run</button>
<button id="clear0">clear</button>

<script src="sample3.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 hasDuplicates = (ary) => {
    let o = {};
    for (let i = 0, max = ary.length; i < max; i += 1) {
        if (o[ary[i]]) {
            return true;
        }
        o[ary[i]] = 1;
    }
    return false;
};

let rotateLetter = (letter, n) => {
    n %= 26;
    n += n < 0 ? 26 : 0;

    let o = letter.codePointAt(0) + n;

    if (/[a-z]/.test(letter)) {
        return String.fromCodePoint(o - ('z'.codePointAt(0) < o ? 26 : 0));
    }
    if (/[A-Z]/.test(letter)) {
        return String.fromCodePoint(o - ('Z'.codePointAt(0) < o ? 26 : 0));
    }
    return letter;
};
let rotateWord = (word, n) =>
    word.split('')
    .map((c) => rotateLetter(c, n))
    .join('');

let reader = new FileReader();

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

    let wordsObj = {};
    
    words.forEach((word) => wordsObj[word] = 1);
    
    Object.keys(wordsObj)
        .sort()
        .forEach((word) => {
            range(1, 26).forEach((n) => {
                let word0 = rotateWord(word, n);
                if (word < word0 && wordsObj[word0]) {
                    p(`${word}, ${word0}, ${n}`);
                }
            });
        });
};
input_file0.onchange = () => {
    p('4.');
    reader.readAsText(input_file0.files[0]);
};

let output = () => {    
    p('3.');
    let nums1 = [1, 2, 3, 4, 5],
        nums2 = [1, 2, 1, 4, 5];

    p(hasDuplicates(nums1));
    p(hasDuplicates(nums2));
};

let clear = () => pre0.textContent = '';

btn0.onclick = output;
btn1.onclick = clear;

output();