javascript生成m位随机数

function ran(m) {
     m = m > 13 ? 13 : m;
     var num = new Date().getTime();
     return num.toString().substring(13 - m);
}
console.log(ran(5));

1 function rand(m) {
2       m = m > 16 ? 16 : m;
3       var num = Math.random().toString();
4       if(num.substr(num.length - m, 1) === '0') {
5            return rand(m);
6      }
7     return num.substring(num.length - m);
8 }
9 console.log(rand(5));

 1 function rando(m) {
 2     var num = '';
 3     for(var i = 0; i < m; i++) {
 4          var val = parseInt(Math.random()*10, 10);
 5          if(i === 0 && val === 0) {
 6                i--;
 7                continue;
 8           }
 9                 num += val;
10      }
11      return num;
12 }
13 console.log(rando(5));