Using Underscore.js to filter an array of objects on a property using a 'contains'

Question

I have an array of objects which I would like to filter using a contains/any method on a property using underscore.

For example, if I had the following variables:

var people = [
{
    name: 'Dave',
    age: 26
},
{
    name: 'Frank',
    age: 23
}];
var allowedAges = [20, 23, 24];

I would like to use underscore to end up with a result like:

 var allowedPeople = [];
 _.each(_.where(people, { age: _.any()}), function (person) {
            allowedPeople.push(person);
        });

And there may also be occasions where allowedAges is an array of objects and id want to use the contains/any on the people array using a property of the objects in allowedAges.

Answer 1

The JS equivalent of contains is usually indexOf (and find in rare cases).

You can use the built-in Array.prototype.filter to do this like:

people.filter(function (person) {
  return allowedAges.indexOf(person.age) !== -1; // -1 means not present
});

or with underscore, using the same predicate:

_.filter(people, function (person) {
  return allowedAges.indexOf(person.age) !== -1; // -1 means not present
}

If you have access to ES6 collections or a polyfill for Set , you can replace the allowedAges array with a set (enforcing unique values) and simply use Set.prototype.has :

people.filter(person => allowedAges.has(person.age))

Answer 2

For the sake of completeness, here's an underscore solution that works with a mixed array of integers and objects containing an age property.

var allowedPeople = _.filter(people, (p) =>
  _.some(allowedAges, (a) => (a.age || a) === p.age)
);

Answer 3

Why not use vanilla js filter ?

var people = [
  {
    name: 'Dave',
    age: 26
  },
  {
    name: 'Frank',
    age: 23
  }
];

var allowedAges = [20, 23, 24];

var allowedPeople = people.filter(function((person, i, arr) {
  return allowedAges.indexOf(person.age) !== -1;
});

Answer 4

This is a pure JS version:

 var people = [{ name: 'Dave', age: 26 }, { name: 'Frank', age: 23 }]; var allowedAges = [20, 23, 24]; function filterData(arr, key, searchList){ var result = []; if(Array.isArray(searchList)){ result = arr.filter(function(item){ return (searchList.indexOf(item[key])>-1); }); } else{ result = arr.filter(function(item){ return (searchList === item[key]); }); } return result; } document.write("<pre>" + JSON.stringify(filterData(people,"age", allowedAges), 0, 4) + "</pre>")