function prime (n) {
        var n = parseInt(n) || 100;
        var arr = [];
        var obj = {};
        for(var i = 1;i <= n;i++){
          obj.i = [];
          for(var j = 1;j <= i;j++){
            if(i%j === 0){
              obj.i.push(j);
            }
          }
          if(obj.i.length <= 2){
            arr.push(i);
          }
        }
        return arr;
      }
      
      console.log(zhishu(100));

思路: 質(zhì)數(shù)是只能被1和自己整除的整數(shù).能通過被整除的次數(shù)來判斷是否是質(zhì)數(shù).

課程上的方法:

        function prime (n) {
        var arr = [];
        var count = 0;
        for(var i = 2;i <= n;i++){
          for(var j = 1;j <= Math.sqrt(i); j++){
            //這里是有算法存在,能減少循環(huán)次數(shù).
            if(i%j === 0){
              count++;
            }
          }
          if(count == 1){
            arr.push(i);
          }
          count = 0;
        }
        return arr
      }