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?
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' } } ]
*/
You can use _.object()
to turn it back into an object.
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.
_.map()
will always return an array, but you can get the behavior with _.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 memo
argument on the first call of the anonymous function:
var regurgitateCars = _.reduce(cars, function(memo, value, key) {
memo[key] = value;
return memo;
}, {});
map
returns an array
so there's no way you could get it to return the original object with out writing your own. See documentation :
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).
There is no way to return a object with the current implementation of map. It's been suggested that the library add a .mapValues()
function which would do what you like. Here's how you would add it to your code:
_.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:
var regurgitate_cars = _.mapValues(cars, function(value, key){
return value;
});
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