Example of method for generating random numbers min and max in js

In this article, we mainly share with you examples of the method of generating random numbers min and max in js, hoping to help everyone.

1. Math (arithmetic) object knowledge of js

Usually the number we hope to get will be an integer

And Math.ceil(), Math.floor(), Both Math.round() and parseInt() can get integers. Now let’s take a look at their differences.

Math.ceil();    //向上取整。
Math.floor();    //向下取整。
parseInt()；    //向下取整。
Math.round();    //四舍五入。
Math.random();    //0.0 ~ 1.0 之间的一个伪随机数。[0,1)  包含0，不包含1。
Math.ceil(Math.random()*10);      // 获取从1到10的随机整数 ，取0的概率极小。当随机数取到0时，才返回0；取到0.1返回的是1。
Math.floor(Math.random()*10);    //可均衡获取0到9的随机整数。
parseInt(Math.random()*10);    //可均衡获取0到9的随机整数。
Math.round(Math.random());     //可均衡获取0到1的随机整数。
Math.round(Math.random()*10);    //基本均衡获取0到10的随机整数，其中获取最小值0和最大值10的几率少一半。

When the random number is 0~0.4, 0 is returned, 0.5~1.4 returns 1...8.5~9.4 returns 9, 9.5~9.9 returns 10. Therefore, the distribution interval of the head and tail is only half that of other numbers.

2. Actual requirements

Generate a random number of [0, max]

Math.floor(Math.random()*(max+1));
parseInt(Math.random()*(max+1));
生成[1，max]的随机数
Math.floor(Math.random()*10)+1;
parseInt(Math.random()*10)+1;
生成[min,max]的随机数
Math.floor(Math.random()*(max-min)+min);
parseInt(Math.random()*(max-min)+min);

3. Function implementation

Get the random number of [min,max] Integer, can be used in js to generate verification code or randomly select an option.

function randomNum(min,max){ 
	switch(arguments.length){ 
		case 1: 
			return parseInt(Math.random()*min+1); 
			break; 
		case 2: 
			return parseInt(Math.random()*(max-min+1)+minNum); 
			break; 
		default: 
			return 0; 
			break; 
	} 
}

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