JavaScript - Serious functions - Anonymous Functions, Scope and Closures(How to use 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. 7060)を取り組んでみる。

SHARPEN YOUR PENCIL(No. 7060)

コード(Emacs)

HTML5

<pre id="output0"></pre>
<button id="run0">run</button>
<button id="clear0">clear</button>
<script src="sample1.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 cookies = {
    instructions: 'Preheat oven to 350…',
    bake: (time) => {
        p('Baking the cookies.');
        setTimeout((time) => {
            p('Cookies are ready, take them out to cool.');
            p('Cooling the cookies.');
            setTimeout(() => p('Cookies are cool, time to eat!')
                       , 1000);
        }, time);
    },
};

let handleButon = () => {
    p('Time to bake the cookies.');
    cookies.bake(2500);
};

let output = () => {
    handleButon();
};

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

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

output();