Comparing multiple objects in two arrays

Question

I have two sets of objects that I am currently pushing to two different arrays and I'm trying to compare both sets of arrays for number of objects and that the value from the key value pairs are correct.

I can successfully compare the lengths of both arrays, but I've tried using straight equality such as orderChart == userInput (which are the variable names of my arrays) but I keep getting a result of false. Any help is appreciated. Thanks!

Ciro Costa · Accepted Answer

What you're trying to perform is deep equality check. If you try to 'naively' comparare two objects only using '==' or '===', it will always return false (as objects in JS are passed by reference).

This is actually a pretty interesting question per se as:

var a = b = {}; 
a === b;  // true
a == b;   // true

var c = {}; var d = {};
c === d; // false
c == d; //false

Anyway ... for checking if an object is equal to another you might want to investigate if the value of each field in the object is equal to the other ones. A question that arises is: what about nested objects? You have to check that either (i.e, use of recursion).

So, one possible solution is:

function equalTo (a, b) {
  if (!(typeof a === 'object') && typeof b === 'object')) 
      || (a === b))
    return true;

  var keysA, keysB, equalKeys;

  keysA = Object.keys(a);
  keysB = Object.keys(b);

  equalKeys = kA.some(function (item, i) {
    return item === kB[i];
  });

  if (!equalKeys)
    return false;

  for (var key in keysA)
    return equalTo(a[keysA[key]], b[keysA[key]]);

  return false;
}

base: we are dealing with non-objects, check for equality with '==='.

recursive: not yet in non-objects, verify if the keys are equal (if not, the objects won't be equal). If they are, for each key, recursively do the check.

edit: as mentioned, both lodash and underscore have an equivalent ::isEqual method (i'd go with lodash)

ps.: this is NOT A TESTED SOLUTION. It is just to illustrate a way of doing (you should go with lodash or other production ready solution)

Comparing multiple objects in two arrays

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