JavaScript - Arrays - Putting Some Order in Your Data(Creating an array from scratch(and adding to it), for loop, forEach, Putting it all together…)

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 4.(Arrays - Putting Some Order in Your Data)、Putting it all together… の EXERCISE(No. 2764) を取り組んでみる。

EXERCISE(No. 2764)

コード(Emacs)

HTML5

<button id="run0">run</button><button id="clear0">clear</button>
<pre id="output0"></pre>

<script src="sample7.js"></script>

JavaScript

let btn0 = document.querySelector('#run0'),
    btn1 = document.querySelector('#clear0'),
    pre0 = document.querySelector('#output0'),
    p = (x) => pre0.textContent += x + '\n';

let getMostCostEffectiveSolution = (scores, costs, highScore) => {
    let cost = 100,
        index = -1;

    scores.forEach((score, i) => {
        if (score === highScore && cost > costs[i]) {
            index = i;
            cost = costs[i];
        }
    });
    return index;
};

let getBestResults = (scores, highScore) => {
    let bestSolutions = [];
    scores.forEach((score, i) => {
        if (score === highScore) {
            bestSolutions.push(i);
        }
    });
    return bestSolutions;
};
let output = () => {
    let scores = [],
        costs = [];

    for (let i = 0; i < 36; i += 1) {
        scores.push(Math.floor(Math.random() * 10));
        costs.push(Math.random());
    }

    let highScore = -1;

    let output;
    scores.forEach((score, i) => {
        output = `Bubble solution #${i} score: ${scores[i]} cost: ${costs[i]}\n`;
        pre0.textContent += output;
        if (score > highScore) {
            highScore = score;
        }
    });

    let cost = getMostCostEffectiveSolution(scores, costs, highScore);
    
    
    p(`Bubbles tests: ${scores.length}`);
    p(`Best solutions: ${getBestResults(scores, highScore)}`);
    p(`Most cost effective solution: ${cost}`);
};

btn0.onclick = output;

btn1.onclick = () => {
    pre0.textContent = '';
};

output();