javascript - 如何根据几个规则过滤数组数组

Question

我有以下数据集作为示例:

const labels = [
  ['Wed', '11 PM'],
  ['Thu', '12 AM'],
  ['Thu', '1 AM'],
  ['Thu', '2 AM'],
  ['Thu', '3 AM'],
  ['Thu', '4 AM'],
  ['Thu', '5 AM'],
  ['Thu', '6 AM'],
];

我正在尝试根据数据数组大小过滤此内容，以每隔 n 小时保留一次，用空字符串替换其他内容。然后我试图只保留一天中有时间的第一个实例。

期望的输出:

[
  ['Wed', '11 PM'],
  ['', ''],
  ['Thu', '1 AM'],
  ['', ''],
  ['', '3 AM'],
  ['', ''],
  ['', '5 AM'],
  ['', ''],
];

我尝试使用一个简单的 for 循环来执行此操作，并检查前一个数组项的日期是否与迭代中的当前日期匹配，但这不起作用，因为它会使字符串为空，然后下一个将与空白字符串而不是原始日期值进行比较。

我认为我需要跟踪循环外某处的第一个天数，然后与之进行比较，这样它就不会改变原始数组？

const labels = [
  ['Wed', '11 PM'],
  ['Thu', '12 AM'],
  ['Thu', '1 AM'],
  ['Thu', '2 AM'],
  ['Thu', '3 AM'],
  ['Thu', '4 AM'],
  ['Thu', '5 AM'],
  ['Thu', '6 AM'],
];

// Want to keep every nth hour, make others empty strings

// Want to keep only the first instance of a day name  that has a time and change the rest of the day names to be empty strings

// Desired output:
// [
//   ['Wed', '11 PM'],
//   ['', ''],
//   ['Thu', '1 AM'],
//   ['', ''],
//   ['', '3 AM'],
//   ['', ''],
//   ['', '5 AM'],
//   ['', ''],
// ];

function hoursLabelInterval(hours) {
  if (hours <= 6) {
    return 1;
  } else if (hours <= 12) {
    return 2;
  } else if (hours <= 24) {
    return 4;
  } else if (hours <= 36) {
    return 6;
  } else if (hours <= 48) {
    return 8;
  } else if (hours <= 60) {
    return 10;
  } else if (hours <= 72) {
    return 12;
  } else {
    return 24;
  }
}
function formatXLabels(labels, hoursToSkip) {
  let result = labels;
  for (let i=1; i<labels.length; i++) {
    if (i%hoursToSkip !== 0) {
      result[i][1] = '';
    }
  }
  console.log(result);
}

formatXLabels(labels, hoursLabelInterval(labels.length));

有什么帮助吗？

Answer 1

可以做这样的事情:

const labels = [
    ['Wed', '11 PM'],
    ['Thu', '12 AM'],
    ['Thu', '1 AM'],
    ['Thu', '2 AM'],
    ['Thu', '3 AM'],
    ['Thu', '4 AM'],
    ['Thu', '5 AM'],
    ['Thu', '6 AM'],
];
let currentDay = '';
const newLabels = labels.map((label, i) => {
    if (i % 2 === 0) {
        if (label[0] !== currentDay) {
        	currentDay = label[0];
            return [label[0], label[1]]
    	}
        return ['', label[1]]
    }
    return ['','']
});

console.log(newLabels);