How to find object properties with the same values among javascript objects?

Question

I would like to find values that are the same among javascript objects (perhaps later also add in a min , max statistic) I got stuck right at the start as my code returns some unexpected output (PS I am not looking for common properties, but for common properties that have the same values)

var obj1 = { "oranges": 5, "apples": 3, "peaches": 1 };
var obj2 = { "oranges": 4, "apples": 3, "peaches": 0 };
var obj3 = { "oranges": 5, "apples": 3, "peaches": 5 };
var obj_common = {};

for (var property in obj1) {
  if (obj1[property] = obj2[property])
    obj_common[property] = obj1[property];
}

console.log(obj_common);

Single "=" is assigning values to variables, == and === are logical (comparison) operators. — Adrian
– Adrian, Commented Sep 3, 2017 at 13:09
Possible duplicate of How to find common properties between JavaScript objects — pedromss
– pedromss, Commented Sep 3, 2017 at 13:22
Thx, I saw that question, but I am not looking for common properties, but for common properties with the same values :) — giorgio79
– giorgio79, Commented Sep 3, 2017 at 16:52

iTob · Accepted Answer · 2017-09-03 13:18:19Z

3

Use == or === for a comparison.

Explanation what your code does: The line (obj1[property] = obj2[property]) assigns the value of obj2[property] to obj1[property]. Because an assignment expression in javascript returns the assigned value, the expression evaluates to true for "oranges" and "apples" (because 4 and 3 are truthy values) and false for "peaches" (because 0 is a falsy value).

answered Sep 3, 2017 at 13:18

iTob

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Ananthakrishnan Baji · Accepted Answer · 2017-09-03 13:22:09Z

0

Please change = to == inside the if statement

= will assign value in right hand side to the variable in left hand side
== will compare value in both sides (eg 1=='1' gives true)
=== use triple = if you want check both value and its type(1==='1' gives false)

var obj1 = { "oranges": 5, "apples": 3, "peaches": 1 };
var obj2 = { "oranges": 4, "apples": 3, "peaches": 0 };
var obj3 = { "oranges": 5, "apples": 3, "peaches": 5 };
var obj_common = {};

for (var property in obj1) {
  if (obj1[property] == obj2[property])
    obj_common[property] = obj1[property];
}

console.log(obj_common);

answered Sep 3, 2017 at 13:22

Ananthakrishnan Baji

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