使用underscore.js进行对象转换

Question

For whatever reason, I have quite a bit of difficulty when trying to transform objects and arrays.

The current data I have is stored in a mongodb collection and looks like this:

[{ "_id" : 1, "name" : "someName", "colorName" : "Pink"},
{ "_id" : 2, "name" : "someName2", "colorName" : "RoyalBlue"},
{ "_id" : 3, "name" : "aThirdOne", "colorName" : "Gold"},
{ "_id" : 4, "name" : "oneMore", "colorName" : "LightGreen"}]

I need to get either the following two arrays, but would like to know how to get both.

[{ "value" : 1, "label" : "someName"},
{ "value" : 2, "label" : "someName2"},
{ "value" : 3, "label" : "aThirdOne"},
{ "value" : 4, "label" : "oneMore"]

[{1 : "someName"},
{2 : "someName2"},
{3 : "aThirdOne"},
{4 : "oneMore"}]

I know it is probably something with _.map , but I am not sure why I can't figure it out. Please advise.

Answer 1

You don't really need Underscore for this, it's just normal Array.prototype.map method usage (although Underscore also provides this method):

 var data = [{ "_id" : 1, "name" : "someName", "colorName" : "Pink"}, { "_id" : 2, "name" : "someName2", "colorName" : "RoyalBlue"}, { "_id" : 3, "name" : "aThirdOne", "colorName" : "Gold"}, { "_id" : 4, "name" : "oneMore", "colorName" : "LightGreen"}]; var result = data.map(function(el, i) { return {value: el._id, label: el.name}; }); document.body.innerHTML = '<pre>' + JSON.stringify(result, null, 4) + '</pre>'; 

Also note, that your second data structure doesn't make sense because it's irregular, so don't use it, it's not very convenient at all.

And here is corresponding Underscore version:

// Or Underscore version
var result = _.map(data, function(el) {
    return {value: el._id, label: el.name};
});

Answer 2

In plain Javascript you can use Array.prototype.forEach() for iteration througt the array and assembling the objects and push it to the wanted results.

The forEach() method executes a provided function once per array element.

 var array = [{ "_id": 1, "name": "someName", "colorName": "Pink" }, { "_id": 2, "name": "someName2", "colorName": "RoyalBlue" }, { "_id": 3, "name": "aThirdOne", "colorName": "Gold" }, { "_id": 4, "name": "oneMore", "colorName": "LightGreen" }], result1 = [], result2 = []; array.forEach(function (a) { result1.push({ value: a._id, label: a.name }); var o = {}; o[a._id] = a.name result2.push(o); }); document.write('<pre>' + JSON.stringify(result1, 0, 4) + '</pre>'); document.write('<pre>' + JSON.stringify(result2, 0, 4) + '</pre>'); 

Answer 3

use:

var newObject = _.map(yourObject, function(val) {
return {
    "value": val._id,
    "label": val.name
}});

And the same concept for the other result you're interested in .