how to pluck objects based on ids using underscore

Question

I have an array that has a bunch of ids

var arr = ["562f464a9cdf7e6e33aa2514","562f464a9cdf7e6e33aa2514"];

and I have an array of objects that looks somewhat like this

[{
    "boatId": "562f464a9cdf7e6e33aa2514",
        "canPoll": true,
}, {
    "boatId": "562f4647e6e33aa2514",
        "canPoll": true,
}]

I want to pluck out the objects from the second list whose ids are not in the array arr

I came up with the following line but it returns false;

var finalBoats = _.map(boats, function (boat) {
    if (originalBoats.length > 0) {
        _.each(originalBoats, function (originalBoat) {
            if (originalBoat === boat.boatId) {
                return boat;
            }
        });
    } else {
        return boat;
    }
});

I also have to account for times that the first array might be empty.

Not sure how I can do this in underscore.

Update : Here is what I want to do exactly

var arr = ["1","2"];

   var unfilteredBoats = [{
        "boatId": "3",
            "canPoll": true,
    }, {
        "boatId": "2",
            "canPoll": true,
    }]

so the extracted array of elements should be

[{
        "boatId": "3",
            "canPoll": true,
    }]

also if arr is empty, it shouldn't filter at all, that part is rather simple.

Tushar · Accepted Answer · 2015-10-28 10:03:50Z

4

You can use filter in VanillaJS

var filteredArr = originalBoats.filter(function(e) {
    return arr.indexOf(e.boatId) === -1;
});

Same can be done using underscore's filter and contains

var filteredArr = _.filter(originalBoats, function(el) {
    return _.contains(arr, el.boatId) === false;
});

Demo

var arr = ["1", "2"];

var unfilteredBoats = [{
  "boatId": "3",
  "canPoll": true,
}, {
  "boatId": "2",
  "canPoll": true,
}];

var filteredArr = unfilteredBoats.filter(function(e) {
  return arr.indexOf(e.boatId) === -1;
});

console.log(filteredArr);

document.getElementById('result').innerHTML = JSON.stringify(filteredArr, 0, 4);

<pre id="result"></pre>

edited Oct 28, 2015 at 10:03

answered Oct 28, 2015 at 9:09

Tushar

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4 Comments

Bazinga777 Over a year ago

Thanks, my goal is to extract the elements from the arr array that are not present in originalBoats

Tushar Over a year ago

@Bazinga777 Can you please add an example of both the arrays, I think the above should work.

Tushar Over a year ago

@Bazinga777 I've added demo, please check

Bazinga777 Over a year ago

You are a life saver. That worked well. Didn't know about the filter property. Thanks

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