生成随机数 ，随机密码

一 、生成[n,m]的随机整数

函数功能：生成[n,m]的随机整数。

在js生成验证码或者随机选中一个选项时很有用

//生成从minNum到maxNum的随机数
function randomNum(minNum,maxNum){ 
    switch(arguments.length){ 
        case 1: 
            return parseInt(Math.random()*minNum+1,10); 
        break; 
        case 2: 
            return parseInt(Math.random()*(maxNum-minNum+1)+minNum,10); 
        break; 
            default: 
                return 0; 
            break; 
    } 
} 

二 、生成n位数的随机密码

function randomPassword(length) {
  length = Number(length)
  // Limit length
  if (length < 6) {
    length = 6
  } else if (length > 16) {
    length = 16
  }
  let passwordArray = ['ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz', '1234567890', '!@#$%&*.'];
  var password = [];
  let n = 0;
  for (let i = 0; i < length; i++) {
    // If password length less than 9, all value random
    if ( password.length < (length - 4) ) {
      // Get random passwordArray index
      let arrayRandom = Math.floor(Math.random() * 4);
      // Get password array value
      let passwordItem = passwordArray[arrayRandom];
      // Get password array value random index
      // Get random real value
      let item = passwordItem[Math.floor(Math.random() * passwordItem.length)];
      password.push(item);
    } else {
      // If password large then 9, lastest 4 password will push in according to the random password index
      // Get the array values sequentially
      let newItem = passwordArray[n];
      let lastItem = newItem[Math.floor(Math.random() * newItem.length)];
      // Get array splice index
      let spliceIndex = Math.floor(Math.random() * password.length);
      password.splice(spliceIndex, 0, lastItem);
      n++
    }
  }
  return password.join("");
}