How to find min/max value in Array of complex objects in Javascript?

Question

Say we have an array:

var antibiotics = [{
    bacteria: "Mycobacterium tuberculosis",
    penicillin: 800,
    streptomycin: 5,
    neomycin: 2,
    gram: "negative"
}, {
    bacteria: "Salmonella schottmuelleri",
    penicillin: 10,
    streptomycin: 0.8,
    neomycin: 0.09,
    gram: "negative"
}, {
    bacteria: "Proteus vulgaris",
    penicillin: 3,
    streptomycin: 0.1,
    neomycin: 0.1,
    gram: "negative"
}, {
    bacteria: "Klebsiella pneumoniae",
    penicillin: 850,
    gram: "negative"
}];

And we want to find minand max of all numerical properties of objects in array (penicillin, streptomycin and neomycin here) assuming values can be null/absent.

How to aggregate such data from an array of objects in JavaScript?

alex · Accepted Answer · 2013-07-24 08:04:26Z

3

You could use Array.prototype.map() to pluck the values you require, and then pass as arguments to Math.max() or Math.min().

Math.max.apply(Math, values);

answered Jul 24, 2013 at 8:04

alex

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2 Comments

Alnitak Over a year ago

don't forget that Math.max.apply will crap out and return NaN if any of the values in the source array are undefined.

DuckQueen Over a year ago

Coulde you eveluete on map() a bit more: how to return more than one value from function we provide to map?

georg · Accepted Answer · 2013-07-24 08:39:13Z

1

Unfortunately, JS standard library doesn't provide Array.max or a "pluck" (=collect) function, but there are many libraries that do, e.g. underscore:

maxPenicillin = _.max(_(antibiotics).pluck('penicillin')))

If you don't like libraries, these function are easy:

Array.prototype.max = function() {
    return this.reduce(function(a, b) {
        return a > b ? a : b;
    })
}

Array.prototype.pluck = function(prop) {
    return this.map(function(x) {
        return x[prop];
    })
}

maxPenicillin = antibiotics.pluck('penicillin').max()

but really, why would you want to reinvent the wheel? Just use a library.

Upd: if I interpret your comment correctly, you're looking for something like this:

var values = {};

_.each(antibiotics, function(x) {
    _.each(x, function(v, k) {
        if(!isNaN(v))
            values[k] = (values[k] || []).concat([v]);
    })
})

var minmax = {};

_.each(values, function(v, k) {
    minmax[k] = [_.min(v), _.max(v)]
})

Result:

{"penicillin":[3,850],"streptomycin":[0.1,5],"neomycin":[0.09,2]}

edited Jul 24, 2013 at 8:39

answered Jul 24, 2013 at 8:12

georg

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2 Comments

DuckQueen Over a year ago

yeah... here problem was to grab all object's (!isNaN(object[prop])) so to have a degree of freedom from property names, and also have all properties values agregated, not just one.

DuckQueen Over a year ago

Point was to get over all statistic - min and max from all Object numeric properties - here [0.09, 850] (as if thay were of same value type representable on chart)

Dragan Okanovic · Accepted Answer · 2013-07-24 08:35:49Z

0

This should do the trick.

http://jsfiddle.net/vgW4v/

Array.prototype.max = function() {
    return Math.max.apply(null, this);
};

Array.prototype.min = function() {
    return Math.min.apply(null, this);
};

And arrays are populated with values if they exist and simply calculated.

Hope this helps.

answered Jul 24, 2013 at 8:35

Dragan Okanovic

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1 Comment

DuckQueen Over a year ago

Good day, Point was to get over all statistic - min and max from all Object numeric properties - here [0.09, 850] (as if thay were of same value type representable on chart)

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