如何限制文本框中的字数

function checkLength(which,remainderNum,maxChars) {
    setTimeout(function() {
		if (which.value.length > maxChars)
			which.value = which.value.substring(0,maxChars);
		var curr = maxChars - which.value.length;
		//document.getElementById().innerHTML = curr.toString();
		$("#"+remainderNum).text(curr);
    }, 100);
}


<div class="theme_con"><label>内容:</label><textarea name="_FSNR" class="theme_text_con" id="fsnrtextarea1"  onpaste="checkLength(this,'remainderNum2',100);"   onkeyup="checkLength(this,'remainderNum2',100);"   onblur="checkLength(this,'remainderNum2',100);"  style="400px;height:100px"></textarea></div>

　　使用了定时函数,主要是因为粘贴的时候,要等粘贴之后才能开始判断字符数.