How to summarize two arrays

Question

This is my first array:

first_arr = [["кстати", 1], ["скажем", 1], ["блин", 1], ["реально", 1], ["вообще", 1], ["допустим", 1], ["фактически", 1], ["получается", 1]]

And the second:

second_arr = [['кстати', 1], ['скажем', 2], ['реально', 3], ['вообще', 3], ['ладно', 5]]

How can I summarize it to be like:

final_arr = [["кстати", 2], ["скажем", 3], ["блин", 1], ["реально", 4], ["вообще", 4], ["допустим", 1], ["фактически", 1], ["получается", 1], ['ладно', 5]]

Answer 1

You can concatenate the two arrays and reduce over it, incrementing the count of each key. Then, call Object.entries on the result:

first_arr = [["кстати", 1], ["скажем", 1], ["блин", 1], ["реально", 1], ["вообще", 1], ["допустим", 1], ["фактически", 1], ["получается", 1]]
second_arr = [['кстати', 1], ['скажем', 2], ['реально', 3], ['вообще', 3], ['ладно', 5]]

const res = Object.entries(first_arr.concat(second_arr).reduce((a, [key, val]) => (a[key] = (a[key] || 0) + val, a), {}))
console.log(res)