jQuery/JavaScript: Filter array with another array

Question

Let's say I have two arrays:

{First: [One, Two, Three], Second: [One, Two, Three], Third: [One, Two, Three]}

[First, Third]

Now I need to remove every key in first array that is not in second array. So - with those two in example - I should be left with:

{First: [One, Two, Three], Third: [One, Two, Three]}

I tried to use $.grep for that, but I can't figure out how to use array as a filter. Help needed! :)

Look, someone asked it before : http://stackoverflow.com/questions/10927722/jquery-compare-2-arrays-return-difference — BENARD Patrick, Sep 19 '13 at 12:11
Given the result, do you mean 'remove every key in the *second* array that is not in the *first* array'? — Rory McCrossan, Sep 19 '13 at 12:12
And that first 'array' is an object with arrays as property values, not an array. — Andy, Sep 19 '13 at 12:13
@Jahnux73 I seek through SO before asking, but didn't found that, thank you! — z-x, Sep 19 '13 at 13:27

score 4 · Answer 1 · answered Sep 19 '13 at 12:19

The fastest way is to create a new object and only copy the keys you need.

var obj = {First: [One, Two, Three], Second: [One, Two, Three], Third: [One, Two, Three]}
var filter = {First: [One, Two, Three], Third: [One, Two, Three]}


function filterObject(obj, filter) {
  var newObj = {};

  for (var i=0; i<filter.length; i++) {
    newObj[filter[i]] = obj[filter[i]];
  }
  return newObj;
}


//Usage: 
obj = filterObject(obj, filter);

score 3 · Answer 2 · answered Sep 19 '13 at 12:44

Other thing you can do without creating a new object is to delete properties

var obj = {First: ["One", "Two", "Three"], Second: ["One", "Two", "Three"], Third: ["One", "Two", "Three"]};
var filter = ["Second", "Third"];


function filterProps(obj, filter) {
  for (prop in obj) {
      if (filter.indexOf(prop) == -1) {
          delete obj[prop];
      } 
  };
  return obj;
};

//Usage: 
obj = filterObject(obj, filter);

jQuery/JavaScript: Filter array with another array

2 Answers2

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