JavaScript - Serious functions - Anonymous Functions, Scope and Closures(take out the anonymous 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 SHARPEN YOUR PENCIL(No. 7472)を取り組んでみる。

SHARPEN YOUR PENCIL(No. 7472)

コード(Emacs)

HTML5

<pre id="output0"></pre>
<button id="run0">run</button>
<button id="clear0">clear</button>
<script src="sample4.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 fn = (food) => {
    if (food === 'cookies') {
        p('More please');
    } else if (food === 'cake') {
        p('Yum yum');
    }
};

let output = () => {
    fn('cookies');
};

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

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

output();