Write a filter in idiomatic javascript

Question

I have this filter, which I don't like:

var products = this.store.filter('product', function(product) {
    var ok = true;
    if (compatibility) {
        ok = ok && product.compatibility == compatibility;
    }
    if (format) {
        ok = ok && product.format == format;
    }
    if (priceRange) {
        ok = ok && product.priceRange == priceRange;
    }
    if (productType) {
        ok = ok && product.productType == productType;
    }
    return ok;
});

Basically, the filter function must return true for products which pass the test, and false for those which don't pass the test. The filter parameters can have a value of be null .

What is the more idiomatic way of rewriting the filter function?

Well, you could use a helper function that compares multiple properties at once which would be more declarative, or convert it to a simple return false on negative cases which'd make the function just 5 lines long. However, I'd pass the code review as is. — Benjamin Gruenbaum
– Benjamin Gruenbaum, Commented Dec 30, 2015 at 20:59
if (compatibility && product.compatibility != compatibility) return; — dandavis
– dandavis, Commented Dec 30, 2015 at 21:03
@gfullam: that's an Ember method to filter elements from the store. Not really related to the question: I am just interested in the filter itself (the function(product) ... part) — blueFast
– blueFast, Commented Dec 31, 2015 at 10:21

Niet the Dark Absol · Accepted Answer · 2015-12-30 21:01:35Z

2

For every test that fails, return false; immediately. There is no point in processing further if you know it's failed.

if( compatibility && product.compatibility != compatibility) {
    return false;
}
// ...
return true;

Alternatively, (hint: don't do this!), you could do a really long one-liner:

return (!compatibility || product.compatibility == compatibility) && (!format || product.format == format) // ...
// interestingly this shortcuts just like the "immediately return false" solution

answered Dec 30, 2015 at 21:01

Niet the Dark Absol

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1 Comment

Ryan Over a year ago

you should maybe put parens around the && expression, even though it doesn't matter

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