求 0 - n 之间的数字之和,
需要把 步骤 写出来
输入: 5 , 输出: 0+1+2+3+4+5 = 15
输入: 0 , 输出: 0=0
输入:-1 , 输出: -1<0
var SequenceSum = (function() {
function SequenceSum() {}
SequenceSum.showSequence = function(count) {
let result = 0
let str = ''
if(count < 0) return count + '<0'
if(count == 0) return count + '=0'
for(let i=0; i<=count; i++){
result += i
if(i == count) continue
str += i + '+'
}
return str += count + ' = ' + result
};
return SequenceSum;