If I have two arrays of objects, like this:
var a1 = [{"a":"b"}, {"b":"c"}, {"d":"e"}],
a2 = [{"g":"h"}, {"a":"b"}, {"i":"j"}]
(note that objects may be of any structure, not so simple)
what is the most efficient way to extract all the objects that are in both arrays?
I checked this question: Finding matches between multiple JavaScript Arrays, but this is not the same...
extract all the objects that are in both arrays?
Basically you just need to combine Simplest code for array intersection in javascript with Object comparison in JavaScript (instead of using the identity == operator):
var intersection = a1.filter(function(a) {
return a2.some(function(b) {
return Object.equals(a, b);
});
});
Use any Object.equals function that fits your requirements best.
what is the most efficient way?
It depends on your objects. If you can define a reasonable compare function on them so that you can sort the arrays, or if you even can come up with a consistent hashing function, there are faster ways than the above. Check the answers in the linked question.
To find only first repetitive object and break the procedure you may use a combination .find methods:
const a1 = [{"a":"b"}, {"b":"c"}, {"d":"e"}], a2 = [{"g":"h"}, {"a":"b"}, {"i":"j"}]
const compareObjects = (o1, o2) => JSON.stringify(o1) === JSON.stringify(o2);
const findFirst = (a1, a2) => a1.find(i1 => a2.find(i2 => compareObjects(i1, i2)));
console.log(findFirst(a2, a1)); // {a: "b"}
You can flatten the objects using JSON.stringify() and then check for intersection.
var a1 = [{"a":"b"}, {"b":"c"}, {"d":"e"}],
a2 = [{"g":"h"}, {"a":"b"}, {"i":"j"}]
// flatten objects in second array
var stringifiedA2 = a2.map(function(x) {
return JSON.stringify(x);
});
// get intersecting objects
var intersecting = a1.filter(function(x) {
return stringifiedA2.indexOf(JSON.stringify(x)) !== -1;
});
intersecting will contain the object {"a": "b"}
JSON.stringify is not bound to preserve any property order, so JSON.stringify({a:1,b:2}) == JSON.stringify({b:2,a:1}) could work or maybe not.
{"a":"b"}is in two arrays...a1[0] === a2[1]isfalse. So, it looks like you are considering two objects as equal if they have the same properties and values, is that correct?