Sum of the first nth term of Series

[hellocan]

Rules:
You need to round the answer upto 2 decimal places and return it as String.
If the given value is 0 then it should return 0.00
You will only be given Natural Numbers as arguments.

Examples:
SeriesSum(1) => 1 = "1"
SeriesSum(2) => 1 + 1/4 = "1.25"
SeriesSum(5) => 1 + 1/4 + 1/7 + 1/10 + 1/13 = "1.57"
Your Test Cases:
Test.assertEquals(SeriesSum(1), "1.00")
Test.assertEquals(SeriesSum(2), "1.25")
Test.assertEquals(SeriesSum(3), "1.39")
Test.assertEquals(SeriesSum(4), "1.49")
where -By
http://www.codewars.com/kata/555eded1ad94b00403000071/train/javascript

[Go7hic]

function seriesSum (num) {
  if (num === 0) {
    return '0.00'
  } else {
    var arr = Array(num)
    for (var n = 0;n < arr.length;n ++) {
      arr[n] = 1/(3*n+1);
    }
    return arr.reduce((i,j) => i+j).toFixed(2)
  }
}

直接看题目写的，觉得下次最好把题目的链接也贴出来。这样做完可以进去看看别人怎么做

[hellocan]

function SeriesSum(n) { 
     if (n) { 
         var arr = []; 
        for (var i = 0; i < n; i++) {
            var l = 1 / (1 + 3 * i);
            arr.push(l);
        }
        return arr.reduce((i, j) => i + j);
    }
} 

[Go7hic]

没有处理 0 的情况，也没有处理两位小数。

格式就是用 Markdown 的格式。

[Go7hic]

这个题目我傻逼了，虽然答案对了，但是我为了想用数组的迭代方法，特意造了个数组来做，其实完全没必要，直接用累加就够了，虽然时间复杂度一样，但是可以省很多代码，哈哈。下面是排名最高的答案

function seriesSum(n) {
  for (var s = 0, i = 0; i < n; i++) {
    s += 1 / (1 + i * 3)
  }
  return s.toFixed(2)
}

[hellocan]

function SeriesSum(n) { 
    if (n===0) {return '0.00';} 
    else{   
        var arr = []; 
        for (var i = 0; i < n; i++) {
            var l = 1 / (1 + 3 * i);
            arr.push(l);
        }
        return arr.reduce((i, j) => i + j).toFixed(2);
    }
}