JavaScript - Starting with the basics - Case Study: Data Structure Selection(Random Words, Bags(Objectss))

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 11(Case Study: Data Structure Selection)の Random Words、Exercise: 6.を JavaScript で取り組んでみる。

Exercise: 6.

cmudict-0.7b.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="sample6.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 reader = new FileReader(),
    emma = {};

let skip = true;
let processLine = (line) => {
    if (line.indexOf('*** START OF THIS PROJECT GUTENBERG EBOOK EMMA ***') !== -1) {
        skip = false;
        return;
    }
    if (skip) {
        return;
    }
    line = line.replace(/[-'/]/g, ' ')
        .replace(/[;:,!?.()"_`”‘“’]/g, '')
        .toLowerCase();
    
    return line.split(/\s+/);
};
Array.prototype.pick = function (n) {
    let result = [],
        a = this.slice();

    range(0, n).forEach(
        () =>result.push(a.splice(Math.floor(Math.random() * a.length), 1))
    );
    return result;
};

reader.onload = () => {
    reader.result
        .split('\n')
        .map((line) => line.trim())
        .filter((line) => line !== '')
        .forEach((line) => {
            let words = processLine(line)
            if (words) {
                 words.forEach((word) => {
                     if (emma[word]) {
                         emma[word] += 1;
                     } else {
                         emma[word] = 1;
                     }
                 });
            }
        });
    output();
};

input_file0.onchange = () => reader.readAsText(input_file0.files[0]);

let output = () => {
    let words = Object.keys(emma);
    if (words.length !== 0) {
        range(0, 5).forEach(() => p(words.pick(10)));
        words.pick(10).forEach((word) => p(word));
        p('keys');
        Object.keys(emma).pick(10).forEach((key) => p(key));
        p('values');
        Object.values(emma).pick(10).forEach((val) => p(val));
        p('key, value');
        Object.keys(emma).pick(10).forEach((key) => p(`${key}: ${emma[key]}`));
    }
};

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

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

output();