javascript自动生成字符串（数字、字符）

<strong>javascript随机生成数字</strong>

主要用到Math.random() 和 Math.floor() 两个函数

Math.random() -- 返回0和1之间的伪随机数 可能为0，但总是小于1，[0,1)

Math.floor()
-- 向下取整，舍掉小数字后的值

实现随机多位数的方法：

/**
	 *<p>
	 *    随机生成数字
	 *</p>
	 *@param num 生成数字位数
	 */
	function randomNumber(num){
		return ''+Math.floor(Math.random() * num) ;
	}

javascript 随机生成字符

以下实例为随机 A-Z / a-z区间 中随机出现的字符

/**
	 *<p>
	 *    随机生成
	 *</p>
	 *@param data json数据 例：{"start":0,"end":2,"number":5,"upper":true} 
	 *@param start  开始下标
	 *@param end    结束下标
	 *@param number 生成位数
	 *@param upper  是否大写 默认为小写
	 */
	function randomLetter(data){
		var letterData = "";
		var lowercase = new Array("a","b","c","d","e","f","g","h","i","g","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z");

		var uppercase = new Array("A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z");
		var start = data.start;
		var end = data.end;
		var number = data.number;
		var upper = data.upper;

		var length = end - start;
		for(var i= 0;i < number; i++){
			var index = Math.floor(Math.random() * length) + start;
			var letter = "";
			if(upper){
				letter = uppercase[index];
			}else{
				letter = lowercase[index];
			}
			letterData += letter;
		}
		return letterData; 
	}

引用

alert(<span style="font-family: Arial, Helvetica, sans-serif;">randomLetter(</span><pre name="code" class="javascript">{"start":0,"end":2,"number":5,"upper":true}

));