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js limit input maximum number of bytes example

小云云Original: 2018-03-17 11:30:211201browse

This article mainly shares with you an example of limiting the maximum number of input bytes in js. After searching for a long time, I finally found a good solution. I hope it can help everyone.

<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<script type="text/javascript" src="../js/jquery-1.9.1.min.js"></script>
	<body>
 		<input type="text" id="nickname" class="nickname" value="" placeholder="请输入您的名字"  onkeyup="limitInputCharLen(this,8);"/>
 		
		<script type="text/javascript">
			function limitInputCharLen(str, maxLen) {
				var w = 0;
				var tempCount = 0;
				//length 获取字数数，不区分汉子和英文 
				for(var i = 0; i < str.value.length; i++) {
					//charCodeAt()获取字符串中某一个字符的编码 
					var c = str.value.charCodeAt(i);
					//单字节加1  
					if((c >= 0x0001 && c <= 0x007e) || (0xff60 <= c && c <= 0xff9f)) {
						w++;
					} else {
						w += 2;
					}
					if(w > maxLen) {
						str.value = str.value.substr(0, i);
						break;
					}
				}
			}
		</script>
	</body>
</html>

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