JavaScript - Starting with the basics - Fruitful Subroutines(Compare)

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 4(Fruitful Subroutines)のExercises(Compare).を JavaScript で取り組んでみる。

Exercises(Compare).

コード(Emacs)

HTML5

<pre id="output0"></pre>
x = <input id="x0" type="number" value="5">
y = <input id="y0" type="number" value="10">
<br>
<button id="run0">run</button>
<button id="clear0">clear</button>

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

JavaScript

let input_x = document.querySelector('#x0'),
    input_y = document.querySelector('#y0'),
    inputs = [input_x, input_y],
    btn0 = document.querySelector('#run0'),
    btn1 = document.querySelector('#clear0'),
    pre0 = document.querySelector('#output0'),
    p = (x) => pre0.textContent += x + '\n',
    range = (start, end, step=1) => {
        let result = [];
        for (let i = start; i < end; i += step) {
            result.push(i);
        }
        return result;
    };

let compare = (x, y) => {
    if (x > y) {
        return 1;
    }
    if (x === y) {
        return 0;
    }
    return -1;
};

let output = () => {
    pre0.textContent = '';
    range(1, 11).forEach((x) => {
        range(1, 11).forEach((y) => {
            p(`compare(${x}, ${y}) => ${compare(x, y)}`);
        })
    });

    let [x, y] = inputs.map((input) => parseInt(input.value, 10));
    
    p(`compare(${x}, ${y}) => ${compare(x, y)}`);
};
    
inputs.forEach((input) => input.onchange = output);
btn0.onclick = output;
btn1.onclick = () => pre0.textContent = '';

output();

x = y =