我有以下for循环,当我使用splice()删除一个项目时,我得到'seconds'是未定义的。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式来做到这一点。他们的愿望是简单地删除一个项目,然后继续前进。

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);
    }           
}

当前回答

删除参数

        oldJson=[{firstName:'s1',lastName:'v1'},
                 {firstName:'s2',lastName:'v2'},
                 {firstName:'s3',lastName:'v3'}]
        
        newJson = oldJson.map(({...ele}) => {
          delete ele.firstName;
          return ele;
          })

它删除和创建新的数组,因为我们在每个对象上使用展开运算符,所以原始数组对象也不会受到损害

其他回答

虽然你的问题是关于从被迭代的数组中删除元素,而不是关于有效地删除元素(除了一些其他处理),但我认为如果遇到类似情况,应该重新考虑它。

这种方法的算法复杂度是O(n^2)作为拼接函数和for循环都遍历数组(在最坏的情况下,拼接函数移位数组的所有元素)。相反,您可以将所需的元素推入到新数组中,然后将该数组赋值给所需的变量(该变量刚刚被迭代)。

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;

自ES2015以来,我们可以使用Array.prototype.filter将所有内容都放在一行中:

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

当您执行.splice()时,数组正在重新索引,这意味着当一个索引被删除时,您将跳过一个索引,并且缓存的.length已过时。

要修复它,你要么需要在.splice()后面递减i,要么简单地反向迭代…

var i = Auction.auctions.length
while (i--) {
    ...
    if (...) { 
        Auction.auctions.splice(i, 1);
    } 
}

这样,重新索引就不会影响迭代中的下一项,因为索引只影响从当前点到数组末尾的项,并且迭代中的下一项低于当前点。

试试吧

RemoveItems.forEach((i, j) => {
    OriginalItems.splice((i - j), 1);
});

这是这个简单线性时间问题的一个简单线性时间解。

当我运行这个代码片段时,n = 100万,每次调用filterInPlace()需要0.013到0.016秒。一个二次解(例如,公认的答案)将需要它的一百万倍左右。

// Remove from array every item such that !condition(item). function filterInPlace(array, condition) { var iOut = 0; for (var i = 0; i < array.length; i++) if (condition(array[i])) array[iOut++] = array[i]; array.length = iOut; } // Try it out. A quadratic solution would take a very long time. var n = 1*1000*1000; console.log("constructing array..."); var Auction = {auctions: []}; for (var i = 0; i < n; ++i) { Auction.auctions.push({seconds:1}); Auction.auctions.push({seconds:2}); Auction.auctions.push({seconds:0}); } console.log("array length should be "+(3*n)+": ", Auction.auctions.length) filterInPlace(Auction.auctions, function(auction) {return --auction.seconds >= 0; }) console.log("array length should be "+(2*n)+": ", Auction.auctions.length) filterInPlace(Auction.auctions, function(auction) {return --auction.seconds >= 0; }) console.log("array length should be "+n+": ", Auction.auctions.length) filterInPlace(Auction.auctions, function(auction) {return --auction.seconds >= 0; }) console.log("array length should be 0: ", Auction.auctions.length)

注意,这只是修改原始数组,而不是创建一个新数组;这样做是有好处的,例如,在数组是程序的单一内存瓶颈的情况下;在这种情况下,您不希望创建另一个相同大小的数组,即使是临时的。

另一个简单的方法是一次消化数组元素:

while(Auction.auctions.length){
    // From first to last...
    var auction = Auction.auctions.shift();
    // From last to first...
    var auction = Auction.auctions.pop();

    // Do stuff with auction
}