Javascript:过滤键的结果

Question

我有以下对象:

var colors = {
key1:"Red",
key2:"Blue",
key3:"Green",
key4:"Black"
}

我也有这个键数组:

var keys = ["key1","key3","key4"]

我想从colors中获取相应的颜色。为此，我编写了代码-

keys.map((key)=>{
var color= colors.filter(x=>x==key);
});

但是我在这里得到错误-

colors.filter is not a function

Answer 1

要提取每个键，map是正确的选项，但您只需要从colors获取相应的值:

var colors=
{
key1:"Red",
key2:"Blue",
key3:"Green",
key4:"Black"
};
var keys = ["key1", "key3", "key4"];
const result = keys.map(key => colors[key]);
console.log(result);

注意，如果某个键不存在，则输出值为undefined。要删除undefined值，请在末尾添加.filter(Boolean)(感谢Roko C. Buljan):

const result = keys.map(key => colors[key]).filter(Boolean);

您的问题是您试图在对象上运行filter。filter不是对象的方法，而是一个数组。如果您想使用filter，一个选择是像这样使用Object.entries(但上面的解决方案要简单得多)。

var colors=
{
key1:"Red",
key2:"Blue",
key3:"Green",
key4:"Black"
};
var keys = ["key1", "key3", "key4"];
const result = Object.entries(colors).filter(([key, color]) => keys.includes(key)).map(([, color]) => color);
console.log(result);

Answer 2

可以使用Array.prototype.reduce()

const colors = {
key1:"Red",
key2:"Blue",
key3:"Green",
key4:"Black"
};
const keys = ["key1", "key3", "key4", "key99"];
const result = keys.reduce((a, k) => (colors[k]&&a.push(colors[k]), a), []);
console.log(result)

注意"key99"不会包含在result数组中

Answer 3

请尝试以下操作:

var colors = {
key1:"Red",
key2:"Blue",
key3:"Green",
key4:"Black"
}

var keys = ["key1","key3","key4"]

let a = keys.map((key)=>{
return colors[Object.keys(colors).filter(x=>x==key)];
});