var people = [
{firstName : "Thein", city : "ny", qty : 5},
{firstName : "Michael", city : "ny", qty : 3},
{firstName : "Bloom", city : "nj", qty : 10}
];
var results=_.pluck(_.where(people, {city : "ny"}), 'firstName');
例如：我需要firstName和qty。
要投影到多个属性，您需要map，而不是采摘：
var results = _.map(
_.where(people, {city : "ny"}),
function(person) {
return { firstName: person.firstName, qty: person.qty };
}
);
[{"firstName":"Thein","qty":5},{"firstName":"Michael","qty":3}]
请注意，如果您愿意，您可以创建一个辅助方法“pluckMany”，它与使用可变参数的 pluck 执行相同的操作：
// first argument is the source array, followed by one or more property names
var pluckMany = function() {
// get the property names to pluck
var source = arguments[0];
var propertiesToPluck = _.rest(arguments, 1);
return _.map(source, function(item) {
var obj = {};
_.each(propertiesToPluck, function(property) {
obj[property] = item[property];
});
return obj;
});
};
您可以使用该_.mixin函数将“pluckMany”函数添加到_命名空间。使用它，您可以简单地编写：
var results = _.chain(people).where({city : "ny"}).pluckMany( "firstName", "qty").value();
TL;DR用途：
var results = _.chain(people)
.where({ city: "ny" })
.map(_.partialRight(_.pick, 'firstName', 'qty'))
.value();
但是请继续阅读以获取解释，因为我觉得找到此解决方案的过程比实际答案更有趣。
一般模式是（它也适用lodash）：
_.map(array, function(obj) { return _.pick(obj, 'x', 'y', 'z'); });
鉴于这个map转换集合的每个元素的通用函数，有多种方法可以适应您的特定情况（这保证了 的灵活性map，这是功能程序的一个非常基本的构建块）。
让我在下面介绍几种实现我们的解决方案的方法：
var _ = require('lodash'); // @lodash 2.4.1 at the time of writing
// use underscore if you want to, but please see http://stackoverflow.com/questions/13789618/differences-between-lodash-and-underscore
/* la data */
var people = [{
firstName: "Thein",
city: "ny",
qty: 5
}, {
firstName: "Michael",
city: "ny",
qty: 3
}, {
firstName: "Bloom",
city: "nj",
qty: 10
}];
/* OPTION1 : mixin' with _ */
_.mixin({
pluckMany: function() {
var array = arguments[0],
propertiesToPluck = _.rest(arguments, 1);
return _.map(array, function(item) {
/* Alternative implementation 1.1
* ------------------------------
* Taken from @mMcGarnagle answer
* _each is easy to understand here,
* but has to modify the variable `obj` from a closure
* I try to avoid that for trivial cases like this one.
*/
var obj = {};
_.each(propertiesToPluck, function(property) {
obj[property] = item[property];
});
return obj;
/* Alternative implementation 1.2
* ------------------------------
* Rewrite the previous code,
* by passing the accumulator (previously`obj`, but really it is an object that accumulates the result being constructed) across function calls.
* This construction is typical of the `reduce` function, closer to a functionnal programming style.
*/
return _.reduce(propertiesToPluck, function(obj, property) {
obj[property] = item[property];
return obj;
}, {});
/* Alternative implementation 1.3
* ------------------------------
* If we are already using lodash/underscore,
* then let's use the `pick` function ! I also included an example of `flatten` here
*/
return _.pick(item, _.flatten(propertiesToPluck, true));
/* Alternative implementation 1.4
* ------------------------------
* But really flatten is not needed.
*/
return _.partial(_.pick, item).apply(null, propertiesToPluck);
});
}
});
/* Let's use our mixed function !
* Since we call several _ functions on the same object
* it is more readable to chain the calls.
*/
var results = _.chain(people)
.where({
city: "ny"
})
.pluckMany('firstName', 'qty')
.value();
/* OPTION 2 : without mixing our code with lodash/underscore */
var results = _.chain(people)
.where({
city: "ny"
})
.map(_.partialRight(_.pick, 'firstName', 'qty'))
.value();
console.log(results);
如果你喜欢这种用underscoreor编写代码的方式lodash，我强烈建议你看看函数式编程，因为这种写作风格以及许多函数（map以及reduce许多其他函数）都来自那里。
注意：这显然是下划线中的常见问题： https ://github.com/jashkenas/underscore/issues/1104
如果这些被排除在下划线/lodash之外，这显然不是偶然的：“可组合性比功能更好”。你也可以说do one thing and do it well。这也是_.mixin存在的原因。
是的，我希望pluck可以选择传递一个数组，但与此同时，你可以这样做：
const pluckFields = (arr, fields) => _.map(arr, item => _.pick(item, fields))
我的理解是问题的作者想要获取具有许多属性的对象数组并将每个对象剥离为一小部分属性。
使用 _ 有无数种方法，但我最喜欢这种方法。传入一个空的结果对象，该对象将是函数内部的“this”。使用 _each 进行迭代，并 _pick 您想要的字段：
var myObjects = [
{ "first" : "eric",
"last" : "gumbo",
"code" : "x482"
},
{ "first" : "john",
"last" : "dinkman",
"code" : "y9283"
}
];
var result = [];
_.each( myObjects, function(itm) { this.push(_.pick(itm,"first","code")) }, result );
console.log(result);
YAAUu -是的另一个答案使用下划线......
// use a proper browser to run this code snippet, a browser that is es6-compliant
let people = [{
firstName: "Thein",
city: "ny",
qty: 5
},
{
firstName: "Michael",
city: "ny",
qty: 3
},
{
firstName: "Bloom",
city: "nj",
qty: 10
}
];
// either you pick the properties you want
let picking = _.iteratee((person) => _(person).pick("firstName", "city"));
// either you omit the properties you do not want
let omitting = _.iteratee((person) => _(person).omit("qty"));
// create the filter by city
let living = (people, city) => _(people).where({
"city": city
});
// put the "filter by city" into a mixin (as I assume it would be used again & again)
_.mixin({
living: living
});
// do the thing (twice),
// these chaining methods could be done into a mixin as well
console.log("results by picking properties:", _(people).chain().living("ny").map(picking).value());
console.log("results by omitting properties:", _(people).chain().living("ny").map(omitting).value());<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>那一个线性可能会节省一些行：
var results=_.pick(_.where(people, {city : "ny"}), 'firstName', 'qty');
我们不必使用 pluck，也可以省略 do the trick。
var result = _.map(people, function(person) {
return _.omit(person, 'city');
});