Javascript TypeError：无法读取未定义的属性“indexOf”
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Javascript TypeError: Cannot read property 'indexOf' of undefined
提问by Ali Hesari
In this code I want to remove an element from the cart_productsarray.
在这段代码中，我想从cart_products数组中删除一个元素。
var cart_products = ["17^1", "19^1", "18^1"];
var product = 17;
$.each(cart_products,function(key, item) {
if(item.indexOf(product+"^") !== -1){
cart_products.splice(key, 1);
}
});
But I get this error in Google Chrome console:
但是我在 Google Chrome 控制台中收到此错误：
Uncaught TypeError: Cannot read property 'indexOf' of undefined
未捕获的类型错误：无法读取未定义的属性“indexOf”
Is there something wrong with the code?
代码有问题吗？
Thanks for your help.
谢谢你的帮助。
回答by T.J. Crowder
The problem is that you're modifyingthe array while jQuery's $.eachis looping over it, so by the time it gets to the end, the entry that used to be at index 2 is no longer there. (I admit I'm a bit surprised $.eachbehaves that way, but I haven't used $.eachin at least five years, so...)
问题是您在jQuery循环遍历数组时正在修改数组$.each，因此当它结束时，曾经位于索引 2 的条目不再存在。（我承认我有点惊讶这样的$.each行为，但我$.each至少有五年没用过了，所以......）
If the goal is to remove matches from the array, the better choice is filter:
如果目标是从数组中删除匹配项，更好的选择是filter：
var cart_products = ["17^1", "19^1", "18^1"];
var product = 17;
cart_products = cart_products.filter(function(item) {
return item.indexOf(product+"^") === -1;
});
console.log(cart_products);...or alternately if it's important to modify the array in-place rather than creating a new one use a boring forloop as Andreas points outlooping backwardthrough the array so it doesn't matter when you remove things:
...或者，如果就地修改数组而不是创建新数组很重要，请使用无聊的for循环，因为 Andreas 指出在数组中向后循环，因此删除内容时无关紧要：
var cart_products = ["17^1", "19^1", "18^1"];
var product = 17;
var target = product + "^";
for (var index = cart_products.length - 1; index >= 0; --index) {
if (cart_products[index].indexOf(target) !== -1) {
cart_products.splice(index, 1);
}
}
console.log(cart_products);回答by shadymoses
First of all, you don't need to use a jQuery each for this. Second, it's not a great idea to alter an array that you are operating on. If you're trying to remove elements from an array, use filter. Filter has the following signature:
首先，您不需要为此分别使用 jQuery。其次，更改您正在操作的数组并不是一个好主意。如果您尝试从数组中删除元素，请使用过滤器。过滤器具有以下签名：
someArray.filter(function(item, index, array) {
// return a value that is truthy to keep an item or falsey to remove it
})
Filter returns a new array with only the values that match what you want. That means you don't mess with your original array, which is a good idea anyways. In your case it would look like this:
Filter 返回一个新数组，其中仅包含与您想要的值匹配的值。这意味着您不会弄乱原始数组，无论如何这是一个好主意。在您的情况下，它看起来像这样：
var filteredProducst = cart_products.filter(function(item) {
return item.indexOf(product + "^")
})
