## 2017年4月22日土曜日

### JavaScript - Starting with the basics - Conditionals and Recursion(Integer Division and Modulo(%), Boolean expressions, Logical Operators(&&, ||), Conditional Execution(if), Alternative Execution(else), Keyboard Input(input element)

Think Perl 6: How to Think Like a Computer Scientist (Laurent Rosenfeld(著)、Allen B. Downey(著)、Oreilly & Associates Inc)のPart 1(Starting with the basics)、Chapter 4(Conditionals and Recursion)のExercises 4-1、2、3.を JavaScript で取り組んでみる。

Exercises 4-1、2、3.

コード(Emacs)

HTML5

```<pre id="output0"></pre>
<ol>
<li>
seconds: <input id="seconds0" type="number" step="1" value="240000">
</li>
<li>
a: <input id="a0" type="number" min="0" step="1" value="1">
b: <input id="b0" type="number" min="0" step="1" value="2">
c: <input id="c0" type="number" min="0" step="1" value="3">
n: <input id="n0" type="number" min="3" step="1" value="4">
</li>
<li>
a: <input id="a1" type="number" step="1" value="1">
b: <input id="b1" type="number" step="1" value="2">
c: <input id="c1" type="number" step="1" value="3">
</li>
</ol>
<button id="run0">run</button>
<button id="clear0">clear</button>

<script src="sample1.js"></script>
```

JavaScript

```let input0 = document.querySelector('#seconds0'),
input_a0 = document.querySelector('#a0'),
input_b0 = document.querySelector('#b0'),
input_c0 = document.querySelector('#c0'),
input_n0 = document.querySelector('#n0'),
input_a1 = document.querySelector('#a1'),
input_b1 = document.querySelector('#b1'),
input_c1 = document.querySelector('#c1'),
btn0 = document.querySelector('#run0'),
btn1 = document.querySelector('#clear0'),
pre0 = document.querySelector('#output0'),
p = (x) => pre0.textContent += x + '\n';

let daysHoursMinutesSeconds = (seconds) => {
let days = Math.floor(seconds / (24 * 60 * 60));
seconds %= (24 * 60 * 60)
let hours = Math.floor(seconds / (60 * 60));
seconds %= (60 * 60)
let minutes = Math.floor(seconds / 60);
seconds %= 60;
p(`days: \${days}, hours: \${hours}, minutes: \${minutes}, seconds: \${seconds}`);
};
let daysHoursMinutesSecondsInput = () => {
let seconds = parseInt(input0.value, 10);

daysHoursMinutesSeconds(seconds);
};

let checkFermat = (a, b, c, n) => {
if ((Math.pow(a, n) + Math.pow(b, n) === Math.pow(c, n)) && n > 2) {
p('Holy smokes, Fermat was wrong!');
} else {
p("No, that doesn't work.");
}
};
let checkFermatInput = () => {
let a = parseInt(input_a0.value, 10),
b = parseInt(input_b0.value, 10),
c = parseInt(input_c0.value, 10),
n = parseInt(input_n0.value, 10);

checkFermat(a, b, c, n);
};

let isTriangle = (a, b, c) => {
if (a >= b + c || b >= c + a || c >= a + b) {
p('No');
} else {
p('Yes');
}
};

let isTriangleInput = () => {
let a = parseInt(input_a1.value, 10),
b = parseInt(input_b1.value, 10),
c = parseInt(input_c1.value, 10);

isTriangle(a, b, c);
};

let output = () => {
p('1-2.');
daysHoursMinutesSeconds(240000);

p('1-3.');
daysHoursMinutesSecondsInput();

p('2-2.');
checkFermatInput();

p('3-2.');
isTriangleInput();
};

btn0.onclick = output;
btn1.onclick = () => pre0.textContent = '';

output();
```

1. seconds:
2. a: b: c: n:
3. a: b: c: