Is array objects subset of array of objects

Question

I'm trying to write a function to check if the array of objects is a subset of another array of objects and I want it to return a boolean.

Here's what I have so far:

var arr1 = [
    { answer: "dispersed", question: "where_is_your_flare_located" },
    { answer: "continuous", question: "what_frequnecy_of_measurement_do_i_require_to_assess_methane_emissions" }
];

var arr2 = [
    { question: 'where_is_your_flare_located', answer: 'dispersed' },
    { question: 'what_frequnecy_of_measurement_do_i_require_to_assess_methane_emissions', answer: 'periodic' },
    { question: 'how_long_is_the_flare_expected_to_be_in_operation', answer: 'n_a' },
    { question: 'am_i_managing_an_existing_flare_or_planning_to_install_a_new_one', answer: 'n_a' },
    { question: 'do_i_have_access_to_assistance_gases', answer: '' },
    { question: 'do_i_have_access_to_purge_gas', answer: '' },
];

var compare = arr2.filter(function(o) {
    var resultQuestion = o.question;
    var resultAnswer = o.question;

    return arr1.some(function(i) {
        var filterQuestion = i.question;
        var filterAnswer = i.question;
        return ((filterQuestion === resultQuestion) && (resultAnswer === filterAnswer));
    });
});

console.log(compare)

I don't understand what I'm doing wrong. I will appreciate any help or explanation.

So you want to return true if all elements in arr1 appear in arr2? — Jamiec
– Jamiec, Commented Dec 7, 2021 at 16:25
"...what I'm doing wrong." - Why do you think there's something wrong with your script? Explain the actual behavior and add any error messages you might see in the console (How do I ask a good question?) — Andreas
– Andreas, Commented Dec 7, 2021 at 16:27
Either a dup, or a useful read: stackoverflow.com/a/48211214/294949. — danh
– danh, Commented Dec 7, 2021 at 16:28
"The filter() method creates a new array with all elements that pass the test implemented by the provided function." — Andreas
– Andreas, Commented Dec 7, 2021 at 16:28
You assign var resultAnswer = o.question; but this should likely be var resultAnswer = o.answer;. You have the same issue with filterAnswer. — h0r53
– h0r53, Commented Dec 7, 2021 at 16:31

Jamiec · Accepted Answer · 2021-12-07 16:30:41Z

3

This is simply a case of seeing if every element in arr1 exists in arr2

var arr1 = [
    { answer: "dispersed", question: "where_is_your_flare_located" },
    { answer: "continuous", question: "what_frequnecy_of_measurement_do_i_require_to_assess_methane_emissions" }
    
    // comment the above and uncomment below to return true 
    //{ answer: "periodic", question: "what_frequnecy_of_measurement_do_i_require_to_assess_methane_emissions" }
];

var arr2 = [
    { question: 'where_is_your_flare_located', answer: 'dispersed' },
    { question: 'what_frequnecy_of_measurement_do_i_require_to_assess_methane_emissions', answer: 'periodic' },
    { question: 'how_long_is_the_flare_expected_to_be_in_operation', answer: 'n_a' },
    { question: 'am_i_managing_an_existing_flare_or_planning_to_install_a_new_one', answer: 'n_a' },
    { question: 'do_i_have_access_to_assistance_gases', answer: '' },
    { question: 'do_i_have_access_to_purge_gas', answer: '' },
];

const isSubset = arr1.every(a1 => arr2.find(a2 => a1.answer == a2.answer && a1.question == a2.question));

console.log(isSubset);

answered Dec 7, 2021 at 16:30

Jamiec

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2 Comments

Peter B Over a year ago

It would be more pure to use .some(), it returns a boolean value, whereas .find() returns the first matching object (which is then treated as a bool). The final result will be the same.

Rafal Adam Krohne Over a year ago

This has worked perfectly for me! Thank you so much!!!!

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