How to partition an array, based on specific array combinations?

Question

I have an array and would like to partition them into chunks based on a given combination of values.

For example, I have an array which contains only two different values, Portrait and Landscape.

['Landscape', 'Landscape', 'Portrait', 'Portrait', 'Landscape', 'Portrait']

The conditions I would like it to be partitioned by, would be

• Chunked array size <= 3.
• Chunk can only have 'Landscape' <= 2.
• 'Landscape' and 'Portrait' cannot be in the same chunk.

So, I'd expect an output like:

[['Landscape', 'Landscape'], ['Portrait', 'Portrait'],['Landscape'], ['Portrait']

Answer 1

You could collect the constraints for a new chunk in an array and check if one of the constraints is true and then add a new chunk to the result set.

var array = ['Landscape', 'Landscape', 'Portrait', 'Portrait', 'Landscape', 'Portrait'],
    constraints = [
        (chunk, v) => v !== chunk[0],
        (chunk, v) => v === 'Landscape' && chunk.length === 2,
        chunk => chunk.length === 3
    ],
    chunks = array.reduce((r, v) => {
        var last = r[r.length - 1];
        if (!last || constraints.some(fn => fn(last, v))) r.push(last = []);
        last.push(v);
        return r;    
    }, []);

console.log(chunks);

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