JavaScript - Input, Processing, and Output(Counting the Number of Characters)

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 2(Input, Processing, and Output)、2(Counting the Number of Characters)を取り組んでみる。

2(Counting the Number of Characters)

コード(Emacs)

<p>
  <label for="input0">
    What is the input string? <input id="input0" type="text" value="Homer">
  </label>
</p>
<p id="output0"></p>
<script src="sample2.js"></script>

var input = document.querySelector('#input0'),
    output = document.querySelector('#output0'),
    s,
    count;

count = function () {
    s = input.value;

    if (s === '') {
        output.innerHTML = 'must enter something';
    } else {
        output.innerHTML = s + ' has ' + s.length + ' characters.';
    }
};

count();

input.onkeyup = count;

What is the input string?