JavaScript - Making Decisions(Blood Alcohol Calculator)

Exercises for Programmers

開発環境

• OS X El Capitan - Apple (OS)
• Emacs (Text Editor)
• JavaScript (プログラミング言語)
• jQuery (Library)
• Safari(Web browser)

Exercises for Programmers: 57 Challenges to Develop Your Coding Skills (Brian P. Hogan 著、Pragmatic Bookshelf)のChapter 4(Making Decisions)、17(Blood Alcohol Calculator)を取り組んでみる。

17(Blood Alcohol Calculator)

コード(Emacs)

<label for="weight0">
  Body weight in pounds: 
</label>
<input id="weight0" type="number" min="0">
<br>
<label for="gender0">
  Gender: 
</label>
<input id="men0" type="radio" name="gender" checked>
<label for="men0">Men</label>
<input id="women0" type="radio" name="gender">
<label for="women0">Woman</label>
<br>
<label for="total0">
  total alcohol consumed, in onces (oz): 
</label>
<input id="total0" type="number" min="0">
<br>
<label for="ratio0">
  The alcohol distribution ratio: 
</label>
<input id="ratio0" type="number" min="0">
<br>
<label for="hours0">
  Number of hours since the last drink: 
</label>
<input id="hours0" type="number" min="0">
<br>
<br>
<div id="output0"></div>

<script src="sample17.js"></script>

(function () {
    'use strict';
    var bac,
        LEGAL_BAC = 0.08,

        input_total = document.querySelector('#total0'),
        input_gender = document.querySelector('#men0'),
        input_weight = document.querySelector('#weight0'),
        input_ratio = document.querySelector('#ratio0'),
        input_hours = document.querySelector('#hours0'),
        inputs = [input_total, input_gender, input_weight, input_ratio,
                  input_hours],
        div_output = document.querySelector('#output0'),
        calc,
        display;

    calc = function () {
        var a = parseFloat(input_total.value),
            w = parseFloat(input_weight.value),
            r,
            h = parseFloat(input_hours.value);

        if (input_gender.checked) {
            r = 0.73;
        } else {
            r = 0.66;
        }
        return (a * 5.14 / w * r) - 0.015 * h;
    };
    display = function () {
        var bac = calc();
        
        div_output.innerHTML =
            'Your BAC is ' + bac + '<br>';
        if (bac < LEGAL_BAC) {
            div_output.innerHTML +=
                'It is legal for you to drive.';
        } else {
            div_output.innerHTML +=
                'It is not legal for you to drive.';
        }
    };

    inputs.forEach(function (input) {
        input.onkeyup = display;
        input.onchange = display;
    });

    display();
}());

Body weight in pounds:
Gender: Men Woman
total alcohol consumed, in onces (oz):
The alcohol distribution ratio:
Number of hours since the last drink: