Count Array Items in Object of Arrays (combined count)

Question

Consider the following object:

const test = {
    foo: ['foo', 'bar', 'foobar'],
    bar: ['foo', 'bar', 'foobar']
    foobar: ['foo', 'bar', 'foobar']
};

How would one go about getting the combined count of all of the items within each of the arrays in the above object?

I am aware that I can do something along the lines of the following:

let count = 0;

Object.values(test).forEach(value => count += value.length);

console.log(count) // Expected result: 9

I am looking for a simpler (cleaner and hopefully one-liner) way of achieving this...

Ben Carey · Accepted Answer · 2020-05-10 15:01:28Z

9

Just get the length of the flat values.

const test = {
    foo: ['foo', 'bar', 'foobar'],
    bar: ['foo', 'bar', 'foobar'],
    foobar: ['foo', 'bar', 'foobar']
};

let count = Object.values(test).flat().length;

console.log(count);

edited May 10, 2020 at 15:01

Ben Carey

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answered May 10, 2020 at 14:55

Nina Scholz

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4 Comments

Ben Carey Over a year ago

Exactly the sort of thing I am looking for! Thank you!! Will test now

Ben Carey Over a year ago

Works perfectly - will accept as soon as I can. This is exactly why I posted this question. I searched Google for certain keywords but could not find anything. The flat method is something I have not come across before... Thank you very much!

Patrick Roberts Over a year ago

Since the question is tagged ES2017 specifically I'd like to point out that Array.prototype.flat() was actually introduced in the ES2019 specification.

Ben Carey Over a year ago

@PatrickRoberts - ah, very interesting! I only tagged ES2017 because I wanted to encourage modern solutions. ES2019 is even better :-D

Qodeer · Accepted Answer · 2020-05-10 15:00:26Z

2

You could use the array reduce, which comes pretty close to a oneliner:

const count = Object.values(test).reduce((acc, cv) =>  acc + cv.length ,0)

answered May 10, 2020 at 15:00

Qodeer

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1 Comment

Patrick Roberts Over a year ago

I like this solution since reduce() is the conventional method choice for aggregation and avoids creating a temporary array like flat().

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