Javascript:如何检查数组中的某些项目

Question

如何检查数组中的项目是否如下:

var dayPartsArr = ['PT','WDM','WDD','EF','WKE'];

也是对象中的键，例如:

 var dayPartsMap = {
   'PT': 'PRIME TIME',
   'WDM': 'WEEKDAY MORNING',
   'WDD': 'WEEKDAY DAYTIME',
   'EF': 'EARLY FRINGE',
   'WKE': 'WEEKEND DAYTIME'
 };

请记住，dayPartsArr 的顺序并不重要。所以如果

var dayPartsArr = ['WKE','PT','WDM','WDD','EF'];

我仍然希望能够使用 dayPartsMap 来检查 dayPartsArr 中的每个项目是否是 dayPartsMap 中的键

Answer 1

忽略订单

忽略顺序，我们可以获取输入数组并将其与键进行比较，如下所示:

var dayPartsArr = ['WDM','PT','WDD','EF','WKE']; //out of order

var dayPartsMap = {
  'PT': 'PRIME TIME',
  'WDM': 'WEEKDAY MORNING',
  'WDD': 'WEEKDAY DAYTIME',
  'EF': 'EARLY FRINGE',
  'WKE': 'WEEKEND DAYTIME'
};

dayPartsArr.every(item => ~Object.keys(dayPartsMap).indexOf(item)); // true

// Compare against an array with a missing key
dayPartsArr = ['WDM','PT','FAKE', 'WDD','EF','WKE'];

dayPartsArr.every(item => ~Object.keys(dayPartsMap).indexOf(item)); // false

Note the ~ is the bitwise NOT operator, it helps with indexOf

上一个答案

您可以将对象的键转换为数组并比较该数组，如下所示:

有关 Object.keys 的更多信息，check MDN here.

var dayPartsArr = ['PT','WDM','WDD','EF','WKE'];

var dayPartsMap = {
  'PT': 'PRIME TIME',
  'WDM': 'WEEKDAY MORNING',
  'WDD': 'WEEKDAY DAYTIME',
  'EF': 'EARLY FRINGE',
  'WKE': 'WEEKEND DAYTIME'
};

// Create the comparison function...
function arraysIdentical(a, b) {
   var i = a.length;
   if (i != b.length) return false;
   while (i--) {
       if (a[i] !== b[i]) return false;
   }
       return true;
};

/// compare!
arraysIdentical(dayPartsArr, Object.keys(dayPartsMap)); // true

arraysIdentical 最初由 Tim Down 建议