假设我有一个对象:
elmo = {
color: 'red',
annoying: true,
height: 'unknown',
meta: { one: '1', two: '2'}
};
我想用它的属性子集创建一个新对象。
// pseudo code
subset = elmo.slice('color', 'height')
//=> { color: 'red', height: 'unknown' }
我怎样才能做到呢?
假设我有一个对象:
elmo = {
color: 'red',
annoying: true,
height: 'unknown',
meta: { one: '1', two: '2'}
};
我想用它的属性子集创建一个新对象。
// pseudo code
subset = elmo.slice('color', 'height')
//=> { color: 'red', height: 'unknown' }
我怎样才能做到呢?
当前回答
值得注意的是,Zod模式在默认情况下会删除未知属性。如果您已经在使用Zod,那么它很可能适合您的开发过程。
https://github.com/colinhacks/zod
import { z } from "zod";
// muppet schema
const muppet = z.object({
color: z.string(),
annoying: z.boolean(),
height: z.string(),
meta: z.object({ one: z.string(), two: z.string() }),
});
// TypeScript type if you want it
type TMuppet = z.infer<typeof muppet>;
// elmo example
const elmo: TMuppet = {
color: "red",
annoying: true,
height: "unknown",
meta: { one: "1", two: "2" },
};
// get a subset of the schema (another schema) if you want
const subset = muppet.pick({ color: true, height: true });
// parsing removes unknown properties by default
subset.parse(elmo); // { color: 'red', height: 'unknown' }
其他回答
虽然它有点啰嗦,但通过使用Array.prototype.reduce,你可以完成其他人在2年前推荐的underscore/lodash。
var subset = ['color', 'height'].reduce(function(o, k) { o[k] = elmo[k]; return o; }, {});
这种方法从另一方面解决了这个问题:而不是获取一个对象并将属性名传递给它来提取,而是获取一个属性名数组并将它们简化为一个新对象。
While it's more verbose in the simplest case, a callback here is pretty handy, since you can easily meet some common requirements, e.g. change the 'color' property to 'colour' on the new object, flatten arrays, etc. -- any of the things you need to do when receiving an object from one service/library and building a new object needed somewhere else. While underscore/lodash are excellent, well-implemented libs, this is my preferred approach for less vendor-reliance, and a simpler, more consistent approach when my subset-building logic gets more complex.
编辑:es7版本相同:
const subset = ['color', 'height'].reduce((a, e) => (a[e] = elmo[e], a), {});
编辑:这也是咖喱的一个很好的例子!让'pick'函数返回另一个函数。
const pick = (...props) => o => props.reduce((a, e) => ({ ...a, [e]: o[e] }), {});
上面的方法非常接近于另一种方法,除了它让你在运行中构建一个“picker”。如。
pick('color', 'height')(elmo);
这种方法的特别之处在于,你可以很容易地将所选的“picks”传递到任何带有函数的对象中,例如Array#map:
[elmo, grover, bigBird].map(pick('color', 'height'));
// [
// { color: 'red', height: 'short' },
// { color: 'blue', height: 'medium' },
// { color: 'yellow', height: 'tall' },
// ]
对象数组
const aListOfObjects = [{
prop1: 50,
prop2: "Nothing",
prop3: "hello",
prop4: "What's up",
},
{
prop1: 88,
prop2: "Whatever",
prop3: "world",
prop4: "You get it",
},
]
创建一个或多个对象的子集可以通过这种方式解构对象来实现。
const sections = aListOfObjects.map(({prop1, prop2}) => ({prop1, prop2}));
我发现最简单的方法,它不会创建不必要的变量,是一个函数,你可以调用,工作原理与lodash相同,如下所示:
pick(obj, keys){
return Object.assign({}, ...keys.map(key => ({ [key]: obj[key] })))
}
例如:
pick(obj, keys){
return Object.assign({}, ...keys.map(key => ({ [key]: obj[key] })))
}
const obj = {a:1, b:2, c:3, d:4}
const keys = ['a', 'c', 'f']
const picked = pick(obj,keys)
console.log(picked)
Pick = (obj, keys) => { 返回对象。分配({},…键。Map (key => ({ (例子):obj(例子) }))) } Const obj = { 答:1, b: 2 c: 3, d: 4 } Const keys = ['a', 'c', 'f'] Const selected = pick(obj, keys) console.log(选)
核心库中没有这样的内置功能,但你可以使用对象解构来实现它…
const {color, height} = sourceObject;
const newObject = {color, height};
你也可以写一个效用函数…
const cloneAndPluck = function(sourceObject, keys) {
const newObject = {};
keys.forEach((obj, key) => { newObject[key] = sourceObject[key]; });
return newObject;
};
const subset = cloneAndPluck(elmo, ["color", "height"]);
像Lodash这样的库也有_.pick()。
打印稿的解决方案:
function pick<T extends object, U extends keyof T>(
obj: T,
paths: Array<U>
): Pick<T, U> {
const ret = Object.create(null);
for (const k of paths) {
ret[k] = obj[k];
}
return ret;
}
输入信息甚至允许自动补全:
Credit to definitelytyping for U extends keyof T trick!
打印稿操场