javascript - 查找数组对象中的中间数字

Question

我有一个数组对象:

var checkin_status = [{
    "startdate":"2015-01-08",
    "totaldays":"4",  
    "roadmap":[
        { "gifttype": "stars", "quantity": 100, "day": 1},
        { "gifttype": "stars", "quantity": 500, "day": 3},
        { "gifttype": "stars", "quantity": 1000, "day": 10},
        { "gifttype": "stars", "quantity": 1200, "day": 20},
        { "gifttype": "stars", "quantity": 2200, "day": 30},
    ]
}];

var checkin_info = checkin_status[0].roadmap;
var total = 0;
for (var i = 0; i < checkin_info.length; ++i){
    total += checkin_info[i].day;
    alert(total);
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

到目前为止，该代码已尝试过，我需要对象添加下一个索引号，例如:day 1+ day 3 = 4 ，那么下一个将是 3 + 10 = 13 等等。我需要的输出类似于 4,13,20,50 。

知道如何做到这一点吗？

Answer 1

这是 for 循环答案:

var checkin_status = [{
  "startdate": "2015-01-08",
  "totaldays": "4",
  "roadmap": [{
    "gifttype": "stars",
    "quantity": 100,
    "day": 1
  }, {
    "gifttype": "stars",
    "quantity": 500,
    "day": 3
  }, {
    "gifttype": "stars",
    "quantity": 1000,
    "day": 10
  }, {
    "gifttype": "stars",
    "quantity": 1200,
    "day": 20
  }, {
    "gifttype": "stars",
    "quantity": 2200,
    "day": 30
  }, ]
}];

var checkin_info = checkin_status[0].roadmap;
var output = [];
for (var i = 1; i < checkin_info.length; ++i) {
  output.push(checkin_info[i - 1].day + checkin_info[i].day);
}
console.log(output);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

这是 jquery 每个答案:

var checkin_status = [{
  "startdate": "2015-01-08",
  "totaldays": "4",
  "roadmap": [{
    "gifttype": "stars",
    "quantity": 100,
    "day": 1
  }, {
    "gifttype": "stars",
    "quantity": 500,
    "day": 3
  }, {
    "gifttype": "stars",
    "quantity": 1000,
    "day": 10
  }, {
    "gifttype": "stars",
    "quantity": 1200,
    "day": 20
  }, {
    "gifttype": "stars",
    "quantity": 2200,
    "day": 30
  }, ]
}];
var checkin_info = checkin_status[0].roadmap;
var output = [];
$.each(checkin_status[0].roadmap, function(index, obj) {
  if (index === 0)
    return;
  output.push(checkin_info[index - 1].day + obj.day);
});
console.log(output);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>