javascript 从 _.map() 返回对象
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Return object from _.map()
提问by ThomasReggi
So the _.map()function in underscore doesn't return an object, but it takes them. Is there any way for it to return the exact same object it takes?
所以_.map()下划线中的函数不返回一个对象，但它接受它们。有没有办法让它返回完全相同的对象？
var _ = require("underscore");
var cars = {
"mom": {
"miles": "6",
"gas": "4"
},
"dad": {
"miles": "6",
"gas": "4"
}
}
var regurgitate_cars = _.map(cars, function(value, key){
return value;
});
/*
[ { miles: '6', gas: '4' }, { miles: '6', gas: '4' } ]
*/
var regurgitate_cars = _.map(cars, function(value, key){
var transfer = {};
transfer[key] = value;
return transfer;
});
/*
[ { mom: { miles: '6', gas: '4' } },
{ dad: { miles: '6', gas: '4' } } ]
*/
回答by EmptyArsenal
You can use _.object()to turn it back into an object.
你可以用_.object()它把它变回一个物体。
var regurgitate_cars = _.object(
_.map(cars, function(value, key){
return [key, value];
})
);
As for doing that directly with _.map, you'd have to rewrite map to do it.
至于直接使用_.map，您必须重写 map 才能做到这一点。
回答by Andrew Clark
_.map()will always return an array, but you can get the behavior with _.reduce():
_.map()将始终返回一个数组，但您可以通过以下方式获得行为_.reduce()：
var regurgitateCars = _.reduce(cars, function(memo, value, key) {
memo[key] = value;
return memo;
}, cars);
Note that this will modify and return the original object, if you wanted a copy you can provide an empty object as the third argument, which will be used as the memoargument on the first call of the anonymous function:
请注意，这将修改并返回原始对象，如果您想要一个副本，您可以提供一个空对象作为第三个参数，它将用作memo第一次调用匿名函数时的参数：
var regurgitateCars = _.reduce(cars, function(memo, value, key) {
memo[key] = value;
return memo;
}, {});
回答by net.uk.sweet
mapreturns an arrayso there's no way you could get it to return the original object with out writing your own. See documentation:
map返回一个，array因此您无法在不编写自己的情况下返回原始对象。请参阅文档：
Produces a new array of values by mapping each value in list through a transformation function (iterator). If the native map method exists, it will be used instead. If list is a JavaScript object, iterator's arguments will be (value, key, list).
通过转换函数（迭代器）映射列表中的每个值，生成一个新的值数组。如果本机 map 方法存在，则将使用它。如果 list 是 JavaScript 对象，则迭代器的参数将为 (value, key, list)。
回答by megawac
There is no way to return a object with the current implementation of map. It's been suggestedthat the library add a .mapValues()function which would do what you like. Here's how you would add it to your code:
没有办法用 map 的当前实现返回一个对象。有人建议图书馆添加一个.mapValues()可以做你喜欢的功能。以下是将其添加到代码中的方法：
_.mixin({
mapValues: function (input, mapper) {
return _.reduce(input, function (obj, v, k) {
obj[k] = mapper(v, k, input);
}, {});
}
});
Now you can use mapValues to return a new object:
现在您可以使用 mapValues 返回一个新对象：
var regurgitate_cars = _.mapValues(cars, function(value, key){
return value;
});
