javascript - Node.js 中 ES5 过滤器的奇怪行为

Question

我正在尝试使用 ES5 过滤下面的数据:filter。

{
        "EmailAddress": "joe@example.com",
        "Name": "",
        "Date": "2009-01-23 06:22:00",
        "State": "Active",
        "CustomFields": [
            {
                "Key": "[FirstName1]",
                "Value": "joe"
            },
            {
                "Key": "[LastName1]",
                "Value": "bloggs"
            }
        ]
}

为了获得第一个 Name ，我尝试了以下代码:

const firstName = subscriber.CustomFields.filter(cf => cf.Key='FirstName1')

但是，在那行代码之后，源更改为(请参阅 LastName1 更改为 FirstName1):

{
        "EmailAddress": "joe@example.com",
        "Name": "",
        "Date": "2009-01-23 06:22:00",
        "State": "Active",
        "CustomFields": [
            {
                "Key": "[FirstName1]",
                "Value": "joe"
            },
            {
                "Key": "[FirstName1]",
                "Value": "bloggs"
            }
        ]
}

我不明白通过过滤器提取数据如何改变源。我在这里忽略了一些基本的东西吗？

Answer 1

您应该使用 == 而不是赋值 (=)。

const firstName = subscriber.CustomFields.filter(cf => cf.Key == 'FirstName1')

let subscriber = { "EmailAddress": "joe@example.com", "Name": "", "Date": "2009-01-23 06:22:00", "State": "Active", "CustomFields": [ { "Key": "[FirstName1]", "Value": "joe" }, { "Key": "[LastName1]", "Value": "bloggs" } ] }

const firstName = subscriber.CustomFields.filter(cf => cf.Key == '[FirstName1]');
console.log(firstName);