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artydev
artydev

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Using our functional utilities for retrieving deep nested properties.

Let's see a practical case of our tiny functional toolbox.

Here, the object we will use :

let pets = [ { petname : "Bill", breed : "poodle", weight: 12, owner : { ownername : "Paul", contribution : { amount : 32, payed : false }, address : { city : "Paris" } } }, { petname : "Maya", race : "pointer", weight: 27, owner : { ownername : "Henri", contribution : { amount : 12, payed : true }, address : { city : "London" } } }, { petname : "Ooper", race : "setter", weight: 20, owner : { ownername : "Nicolas", contribution : { amount : 12, payed : true }, address : { city : "London" } } } ]
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Say you want the list of all the cities.

With our tools, we can create a function which, when given a 'string path' for a property, returns the property value.

Let's name this function pick.

Here is a possible implementation :

 function pick (path) { let pickprops = map((prop) => pickprop(prop), path.split(".")); return pipe(...pickprops); }
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We can now create a function, which will return a 'city value' for a single entry.

 let pickCity = pick("owner.address.city");
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Nice isn't it ?

Now we can explicitely list all the cities :

 let pickCity = pick("owner.address.city"); let cities = map(pickCity)(pets); // or cities = map(pickCity, pets); console.log(cities)
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I like this one too :

 let cityMapper = map(pick("owner.address.city")); let cities = cityMapper(pets); console.log(cities)
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We can go a step further and feel the spirit of functional programming :

 let mapper = compose(map, pick); let citymapper = mapper("owner.address.city") cities = citymapper(pets) console.log(cities)
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Result :

Image description

You can play with a demo here Demo

Hope you enjoyed...

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