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I am trying to notify user about his medication 3 times daily So I created:

let timesPerDay = []

const today = moment();
//not working
for (let i = 0; i < 3; i++) {
  timesPerDay.push(today.add(8 * i, "hour"));
}
//working normally
for (let i = 0; i < 3; i++) {
  console.log(today.add(8 * i, "hour"));
}

console.log(timesPerDay)
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.min.js"></script>

But there is a weird bug that when pushing to array it saves the first date for every iteration not adding 8 hours to it every time, that's so weird!

How Array.push is working?

Is JavaScript too fast in creating the array so the first loop is not working but the second is working?

CodePen: https://codepen.io/microsmsm-the-flexboxer/pen/BaypYVO

Edit:

Same Snipped I am using after answers is not working

https://codepen.io/microsmsm-the-flexboxer/pen/KKwaoeM

enter image description here

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4

3 回答 3

1

发生这种情况是因为您使用相同的时刻对象来推动所以这应该会有所帮助

let timesPerDay = []

for (let i = 0; i < 3; i++) {
  timesPerDay.push(moment().add(8*i,"hour"));
}

for (let i = 0; i < 3; i++) {
  console.log(moment().add(8*i,"hour"));
}

console.log(timesPerDay)

于 2019-12-18T15:49:01.390 回答
1

逐步引导您完成代码：

let timesPerDay = [] // create an array

const today = moment(); // create a moment object

for (let i = 0; i < 3; i++) {
  // add hours to moment object
  // push a reference to that moment object into your array
  // it's always a reference to the SAME moment object, so the same object is referenced in your array multiple times
  // mutations to that object will show everywhere it is referenced
  timesPerDay.push(today.add(8 * i, "hour")); 
}

for (let i = 0; i < 3; i++) {
  // add hours to same moment object
  // log the string representation of that object AT EACH ITERATION
  // once transformed to a string, the string representation will not change as it is no longer part of the object
  console.log(today.add(8 * i, "hour"));
}

console.log(timesPerDay) // log string representation of your array, which is just 3 references to the same object
于 2019-12-18T16:12:44.460 回答
0

由于 momentjs.add正在改变today变量，因此所有日期都将相同（等于开始日期 + 0 + 8 + 16 小时），因为您一直在推送相同的参考。

您必须克隆日期才能重新开始。

const today = moment()
console.log(`Today: ${today}`)
// Today: Wed Dec 18 2019 17:14:11 GMT+0100
// Loop 0: Wed Dec 18 2019 17:14:11 GMT+0100
// Loop 1: Thu Dec 19 2019 01:14:11 GMT+0100
// Loop 2: Thu Dec 19 2019 09:14:11 GMT+0100
const times = [0, 1, 2].map(offset => {
    const date = moment(today) // clone
    date.add(8*offset,"hour")
    console.log(`Loop ${offset}: ${date}`)
    return date
})

编辑：不是 + 8 + 16 + 24 而是 0 + 8 + 16

编辑2：证明console.log的第二次迭代没有输出OP想要的：

let timesPerDay = []

const today = moment();
console.log(`today: ${today}`)

// today: Wed Dec 18 2019 17:03:02 GMT+0100
// Loop 0: Wed Dec 18 2019 17:03:02 GMT+0100
// Loop 1: Thu Dec 19 2019 01:03:02 GMT+0100
// Loop 2: Thu Dec 19 2019 17:03:02 GMT+0100
// Last loop is 24 hours later than the initial date!
for (let i = 0; i < 3; i++) {
  // Mutates your start date
   const newDate = today.add(8*i,"hour");
   timesPerDay.push(newDate);
   console.log(`Loop ${i}: ${newDate}`);
}

console.log(timesPerDay)
于 2019-12-18T15:50:25.023 回答