js求数组的每一项累加前一项

var baseArr = [1,0,8,9,0,4];
    // 求数组的每一项累加前一项
    // 求得 baseArr = [1,1,9,18,18,22]
    var setArr = [];
    var currNum = 0;
    baseArr.forEach((item, index) => {
      if(index == 0){
        setArr.push(baseArr[index]);
      }else{
          if(currNum){
            currNum = baseArr[index] + currNum;
          }else{
            currNum = baseArr[index] + baseArr[index-1];
          }
          setArr.push(currNum);
      }
    })
    console.log('setArr',setArr) //[1,1,9,18,18,22]