Dynamically filter array of objects based on array of ranges

Question

I am currently writing a class to filter objects within an array. One of the internal methods of this class needs to test to see if a specific property satisfies any of the 'ranges' passed in an array.

Consider the following filter object:

const filters = {
    duration: ['<30', '>30<60', '>300<900', '>900<1800', '>1800', '>60<300']
};

Now consider the following items array (and objects):

const items = [
    {
        duration: 10
    },
    {
        duration: 500
    },
    {
        duration: 10000
    }
];

I need to write a function that will dynamically generate the tests that will compare the value of items[x].duration to each of the ranges defined in filters.duration.

Using the above data as an example, the expected result would be:

[
    {
        duration: 10
    },
    {
        duration: 500
    }
];

I already have the logic for applying the filters. This is what I have so far:

/**
 * Filter the item by duration.
 *
 * @param {object} item
 * @param {array} values
 * @returns {boolean}
 */
_filterByDuration(item, values) {

    // NOTES FOR SO:
    // `item` represents the item to test
    // `values` represents the supplied range e.g. ['<30', '>1800', '>60<300']

    // If any of them match then return `true`
    return values.some( range => {

        range = this._rangeHelper(range);

        // Stuck here...
        // Need to test `item.duration` against the `range` values

    });

}

/**
 * Extract a testable range from the supplied string.
 *
 * @param {string} range
 * @returns {object}
 */
_rangeHelper(range) {

    // Can't decide whether to return an object/array
    // Most likely need a regex to build the dynamic
    // range

}

Update 1

Thinking more about this, I think the best method is to extract the range from the supplied range strings and return an object like so:

{
    min: 0,
    max: 0
}

With this in mind, _rangeHelper should return the following:

For <20:

{
    max: 20
}

For <1800:

{
    min: 1800
}

For >60<300:

{
    min: 60,
    max: 300
}

I think this will then make it fairly simply to just test between the ranges using the range.min and range.max values.

Update 2

Might be guilty of answering my own question shortly... Still keen to hear other ideas though. This is my latest update:

/**
 * Extract a testable range from the supplied string.
 *
 * @param {string} range
 * @returns {object}
 */
_rangeHelper(range) {

    const min = range.match(/>(\d+)/);
    const max = range.match(/<(\d+)/);

    return {
        min: min && typeof min[1] !== 'undefined' ? min[1] : null,
        max: max && typeof max[1] !== 'undefined' ? max[1] : null
    };

}

I'm not sure where these filters are comming from "database" or "hardcoded" but if they're hard coded you could make them functions instead like this const filters = [ (x) => x < 60, (x) => x < 50 && x > 100] I've just made up some functions here but you could put anything you like in those functions — Max Carroll
– Max Carroll, Commented Jun 18, 2020 at 0:49
@MaxCarroll - Unfortunately not as simple as that - the ranges are dynamically generated. Not a problem though as I have basically solved it. I'll leave the question up in case anyone has begun to write an answer - keen to see what other's come up with — Ben Carey
– Ben Carey, Commented Jun 18, 2020 at 0:51

Dmitriy Godlevski · Accepted Answer · 2020-06-18 00:51:43Z

2

Consider this:

let value = 70;
let filters = ['<30', '>30<60', '>300<900', '>900<1800', '>1800', '>60<300'];

function matchRange(value, range){
    const edges = range.match(/[\<\>]\d*/g);

    return edges.every(edge => {
        const [, comp, num] = edge.match(/([\<\>])(\d*)/);
        return comp == '>' ? value > Number(num) : value < Number(num); 
    })
}

filters.some( range => matchRange( value, range ) );

answered Jun 18, 2020 at 0:51

Dmitriy Godlevski

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1 Comment

Ben Carey Over a year ago

This is an interesting answer - slightly different to mine but still achieves the same. +1 and will accept :-D

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