JavaScript - Starting with the basics - Arrays and Lists - Other Ways to Modify an Array(pop, unshift, push, delete, splice, index, length, undefined)

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 9(Arrays and Lists)の Exercise: Mapping and Filtering the Elements of a List.を JavaScript で取り組んでみる。

Exercise: Other Ways to Modify an Array.

コード(Emacs)

HTML5

<pre id="output0"></pre>
<label for="n0">n = </label>
<input id="n0" type="number" step="1" value="100">
<button id="run0">run</button>
<button id="clear0">clear</button>

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

JavaScript

let btn0 = document.querySelector('#run0'),
    btn1 = document.querySelector('#clear0'),
    pre0 = document.querySelector('#output0'),
    input_n = document.querySelector('#n0'),
    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 output = () => {
    let input = range(1, 11),
        n = parseInt(input_n.value, 10);

    input.unshift(n);

    p(input.map((x) => x * x));

    p(input.filter((x) => Math.sqrt(x) *  Math.sqrt(x) === x));
};

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

output();

n =