JavaScript Array.prototype.filter()无法正常工作 [英] Javascript Array.prototype.filter() not working

问题描述

我在客户端运行的这段代码可以过滤事件列表:

I have this piece of code running on the client that filters a list of events:

if (res)
{
    eventList.filter(function(event) {

        const out = res.find(function(visibility) { return visibility.ID == event.id; }) == undefined;
        return out;
    });

    alert(eventList);
}

displayEvents(eventList);

问题在于，即使out是false，该元素也不会被滤除.

The problem is that even when out is false the element is not filtered out.

仅出于调试目的，无论如何我都会尝试return false，结果数组仍然具有所有初始元素:

Just for debug I tried to return false in any case and the resulting array still had all the initial elements:

eventList.filter(function(event) {

    return out;
});

我在这里做错什么了吗?

What am I doing wrong here??

res是服务器返回的JSON对象数组(仅包含ID字段)，而eventList是Facebook事件列表，已从Facebook API请求传递给此回调函数

res is an array of JSON objects (containg only ID field) returned by the server, while eventList is a list of Facebook events, passed to this callback function from a Facebook API request

推荐答案

Array.prototype.filter不会更改数组的原位，而是返回由满足所提供谓词的项目组成的新数组.看起来应该像这样

Array.prototype.filter does not change array inplace, it returns new array made of items that satisfies the provided predicate. It should look like this

var result = eventList.filter(function(event) {
    return res.find(function(visibility) { return visibility.ID == event.id; }) === undefined;
});

您无需先声明和分配变量，然后再从函数中将其返回，您只需返回表达式即可

You don't need to declare and assign variable and then return it from function, you can simply return expression

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