Javascript 检查字符串是否只包含特定字符

Question

如果给定字符串只有某个字符但该字符出现任意次数，我想返回 true。
示例:

// checking for 's'
'ssssss' -> true
'sss s'  -> false
'so'     -> false

Answer 1

检查这个

<div class="container">
    <form action="javascript:;" method="post" class="form-inline" id="form">
        <input type="text" id="message" class="input-medium" placeholder="Message" value="Hello, world!" />

        <button type="button" class="btn" data-action="insert">Show</button>

    </form>
</div>

JavaScript

   var onloading = (function () {

            $('body').on('click', ':button', function () {
                var a = document.getElementById("message").value;
                var hasS = new RegExp("^[s\s]+$").test(a);
                alert(hasS);
            });

    }());

示例 http://jsfiddle.net/kXLv5/40/