JavaScript - Serious functions - Anonymous Functions, Scope and Closures(Closing a function)

Head First JavaScript Programming

開発環境

• macOS Sierra - Apple (OS)
• Emacs (Text Editor)
• JavaScript (プログラミング言語)
• Safari(Web browser)

Head First JavaScript Programming (Eric T. Freeman (著)、Elisabeth Robson (著)、O'Reilly Media)の Chapter 11.(Serious functions - Anonymous Functions, Scope and Closures)の EXERCISE(No. 7371)を取り組んでみる。

EXERCISE(No. 7371)

コード(Emacs)

HTML5

<pre id="output0"></pre>
<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'),
    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 makePassword = (password) =>
    (passwordGuess) => passwordGuess === password,
    multN = (n) => (m) => m * n;

let output = () => {
    let pwd1 = makePassword('password1'),
        pwd2 = makePassword('password2');

    p(pwd1('password1'));
    p(pwd2('password1'));
    p(pwd1('password2'));
    p(pwd2('password2'));

    let multFive = multN(5),
        multTen = multN(10);

    p(multFive(2));
    p(multFive(3));
    p(multTen(2));
    p(multTen(3));
};

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

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

output();