Javascript计算重复项和唯一性并添加到数组中 [英] Javascript count duplicates and uniques and add to array

问题描述

我正在尝试计算日期数组中的重复项，并将其添加到新数组中.

I'm trying to count duplicates in an array of dates and add them to a new array.

但是我只得到重复项和它们在数组中存在的时间.

But i'm only getting the duplicates and the amount of times they exist in the array.

我想要的是:

[a, a, b, c, c] => [a: 2, b: 1, c: 2]

代码:

$scope.result = { };
    for(var i = 0; i < $scope.loginArray.length; ++i) {
        if(! $scope.result[$scope.loginArray[i]]){
             $scope.result[$scope.loginArray[i]] = 0;
        ++ $scope.result[$scope.loginArray[i]];}
    }

有什么建议吗?

推荐答案

为此，您可能需要一个对象，而不是数组.因此，您的工作已经很不错了，但是if的条件搞砸了:

You might need an object for this, not an array. So what you are doing is already great, but the if condition is messing up:

$scope.result = {};
for (var i = 0; i < $scope.loginArray.length; ++i) {
  if (!$scope.result[$scope.loginArray[i]])
    $scope.result[$scope.loginArray[i]] = 0;
  ++$scope.result[$scope.loginArray[i]];
}

代码段

var a = ['a', 'a', 'b', 'c', 'c'];
var r = {};
for (var i = 0; i < a.length; ++i) {
  if (!r[a[i]])
    r[a[i]] = 0;
  ++r[a[i]];
}
console.log(r);

或者以更好的方式，您可以像其他人一样使用.reduce.一个简单的reduce函数将是:

Or in better way, you can use .reduce like how others have given. A simple reduce function will be:

var a = ['a', 'a', 'b', 'c', 'c'];
var r = a.reduce(function(c, e) {
  c[e] = (c[e] || 0) + 1;
  return c;
}, {});

console.log(r);

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