常用

function str (len = 16) {
const str = 'qwertyuioplkjhgfdsazxcvbnm1092837465POLKMNIJUHBYGVTFCRDXZSEWQA';
let sum = '';
for (let i = 0; i< len; i++) {
sum += str.substr(Math.round(Math.random() * 62), 1)
};
return sum;
}