Question

我是初学者，而且我已经被困了好几个小时。我有一个简单的for循环问题。我想要一个警告框，它给出了玩家控制的条形图的总和（它是简单桌面游戏代码的一部分）

这是我的代码：

    var districts = [{bars:0}, {bars:2}, {bars:2}, {bars:3}, {bars:0}, {bars:3}]; //these are all the districts in the game + the amount of bars on them
    var PlayerControlledDistricts = [districts[0], districts[2], districts[3]]; //these are the 3 districts the player controlls
    var AmountOfBars = 0;
    for (i = 0; i <=PlayerControlledDistricts.length; i++){
             AmountOfBars += parseInt(PlayerControlledDistricts[i].bars, 10);
             }
    alert(AmountOfBars);

这段代码有什么问题？如果我把一个警告框放在for循环中我得到：0,2,5 - 所以我认为循环内部的一切都很好 - 但是一旦我把警报放在循环外面就没有任何事情发生......

Answer 1

问题是你循环了太多元素，使用<代替<=

var districts = [{bars:0}, {bars:2}, {bars:2}, {bars:3}, {bars:0}, {bars:3}]; //these are all the districts in the game + the amount of bars on them
var PlayerControlledDistricts = [districts[0], districts[2], districts[3]]; //these are the 3 districts the player controlls
var AmountOfBars = 0;
for (i = 0; i < PlayerControlledDistricts.length; i++){
         AmountOfBars += parseInt(PlayerControlledDistricts[i].bars, 10);
}
alert(AmountOfBars);

Here is a working example

正如@Jamiec指出的那样，你实际上并不需要解析数字，因为你已经把它作为一个数字，所以就这样做：

AmountOfBars += PlayerControlledDistricts[i].bars;

Answer 2

您需要使用<代替<=！

＆＃13;

var districts = [{bars:0}, {bars:2}, {bars:2}, {bars:3}, {bars:0}, {bars:3}]; //these are all the districts in the game + the amount of bars on them
var PlayerControlledDistricts = [districts[0], districts[2], districts[3]]; //these are the 3 districts the player controlls
var AmountOfBars = 0;
for (i = 0; i < PlayerControlledDistricts.length; i++) {
  debugger;
  AmountOfBars += parseInt(PlayerControlledDistricts[i].bars, 10);
}
alert(AmountOfBars);

＆＃13;

Answer 3

将您的更改为：

for (i = 0; i < PlayerControlledDistricts.length; i++)`

这是因为一个数组从0开始，其长度从1开始，你需要计算最多PlayerControlledDistricts.length，因为PlayerControlledDistricts.length本身比数组本身的索引高1。 / p>

Answer 4

问题在于你的迭代 - 你正在迭代到i <=PlayerControlledDistricts.length，这比你需要的多一个，所以最后在最后一个未定义的循环上要求PlayerControlledDistricts[3]。您也不需要parseInt，因为您已经有了数值。这是一个使用console.log的工作示例：

var districts = [{bars:0}, {bars:2}, {bars:2}, {bars:3}, {bars:0}, {bars:3}]; //these are all the districts in the game + the amount of bars on them
var PlayerControlledDistricts = [districts[0], districts[2], districts[3]]; //these are the 3 districts the player controlls
var AmountOfBars = 0;
for (i = 0; i < PlayerControlledDistricts.length; i++) {
         AmountOfBars += PlayerControlledDistricts[i].bars;
}
console.log(AmountOfBars);

JSFiddle：http://jsfiddle.net/eofbenw2/

Answer 5

数组的索引是问题，因为请记住数组的元素应该是0 .....到n-1，因为length属性有n个元素。所以如果你有一个包含10个元素的数组，那么长度将是10，并且元素存储在0到9之间。

之后，这是一个很好的做法，用for for for var for（var i = 0; condition; increment）;

另外，您不需要转换。

我建议您使用Console.log方法验证信息和对象，在Web浏览器的控制台中打印控制台（您可以在控制台选项卡中使用F12进行观看）。

var districts = [{bars:0}, {bars:2}, {bars:2}, {bars:3}, {bars:0}, {bars:3}]; //these are all the districts in the game + the amount of bars on them
var PlayerControlledDistricts = [districts[0], districts[2], districts[3]]; //these are the 3 districts the player controlls
var AmountOfBars = 0;
for (var i = 0; i <PlayerControlledDistricts.length; i++)
        AmountOfBars += PlayerControlledDistricts[i].bars;

alert(AmountOfBars);

此致

对于循环-2阵列

5 个答案: