遍历数组并删除项目，而不会中断循环

本文翻译自：Looping through array and removing items, without breaking for loop

I have the following for loop, and when I use splice() to remove an item, I then get that 'seconds' is undefined. 我有以下for循环，当我使用splice()删除项目时，然后得到“ seconds”是不确定的。 I could check if it's undefined, but I feel there's probably a more elegant way to do this. 我可以检查它是否未定义，但我觉得可能有一种更优雅的方法。 The desire is to simply delete an item and keep on going. 我们的愿望是简单地删除项目并继续进行。

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for (i = 0, len = Auction.auctions.length; i < len; i++) {
    auction = Auction.auctions[i];
    Auction.auctions[i]['seconds'] --;
    if (auction.seconds < 0) { 
        Auction.auctions.splice(i, 1);
    }           
}

#1楼

参考：https://stackoom.com/question/fSpg/遍历数组并删除项目-而不会中断循环

#2楼

Although your question is about deleting elements from the array being iterated upon and not about removing elements (in addition to some other processing) efficiently, I think one should reconsider it if in similar situation. 尽管您的问题是关于从要迭代的数组中删除元素，而不是有效地删除元素（除了某些其他处理），但我认为如果处于类似情况，则应该重新考虑它。

The algorithmic complexity of this approach is O(n^2) as splice function and the for loop both iterate over the array (splice function shifts all elements of array in the worst case). 这种方法的算法复杂度是O(n^2)因为剪接函数和for循环都在数组上迭代（在最坏的情况下，剪接函数会移动数组的所有元素）。 Instead you can just push the required elements to the new array and then just assign that array to the desired variable (which was just iterated upon). 相反，您可以将所需的元素推到新数组中，然后将该数组分配给所需的变量（刚刚对其进行迭代）。

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var newArray = [];
for (var i = 0, len = Auction.auctions.length; i < len; i++) {
    auction = Auction.auctions[i];
    auction.seconds--;
    if (!auction.seconds < 0) { 
        newArray.push(auction);
    }
}
Auction.auctions = newArray;

Since ES2015 we can use Array.prototype.filter to fit it all in one line: 从ES2015开始，我们可以使用Array.prototype.filter使其全部适合一行：

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Auction.auctions = Auction.auctions.filter(auction => --auction.seconds >= 0);

#3楼

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Auction.auctions = Auction.auctions.filter(function(el) {
  return --el["seconds"] > 0;
});

#4楼

This is a pretty common issue. 这是一个很常见的问题。 The solution is to loop backwards: 解决方案是向后循环：

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for (var i = Auction.auctions.length - 1; i >= 0; i--) {
    Auction.auctions[i].seconds--;
    if (Auction.auctions[i].seconds < 0) { 
        Auction.auctions.splice(i, 1);
    }
}

It doesn't matter if you're popping them off of the end because the indices will be preserved as you go backwards. 是否从头开始弹出都没关系，因为索引将在您向后移动时保留。

#5楼

Try to relay an array into newArray when looping: 循环时尝试将数组中继到newArray中：

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var auctions = Auction.auctions;
var auctionIndex;
var auction;
var newAuctions = [];

for (
  auctionIndex = 0; 
  auctionIndex < Auction.auctions.length;
  auctionIndex++) {

  auction = auctions[auctionIndex];

  if (auction.seconds >= 0) { 
    newAuctions.push(
      auction);
  }    
}

Auction.auctions = newAuctions;

#6楼

Here is another example for the proper use of splice. 这是正确使用接头的另一个示例。 This example is about to remove 'attribute' from 'array'. 本示例将要删除“数组”中的“属性”。

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for (var i = array.length; i--;) {
    if (array[i] === 'attribute') {
        array.splice(i, 1);
    }
}

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