memo.xight.org

function grep (pattern) {
	try {
		regex = new RegExp(pattern, "i");
		spans = document.getElementsByTagName('span');
		for (i = 0; i < spans.length; i++) {
			e = spans[i];
			if (e.className == "line" && e.innerHTML.match(regex)) {
				e.style.display = "inline";
			} else {
				e.style.display = "none";
			}
		}
	} catch (e) {
		// 正規表現の文法エラーを無視する
	}
}

<form>
<input type="text" name="pattern" onkeyup="grep(this.value)">
</form>

<form onsubmit="grep(this.pattern.value); return false;">
<input type="text" name="pattern">
</form>