_.object.selectors.js.md

object.selectors

Functions to select values from an object.

accessor

Signature: _.accessor(field:String)

Returns a function that will attempt to look up a named field in any object that it is given.

var getName = _.accessor('name');

getName({ name: 'Seneca' });
// => 'Seneca'

dictionary

Signature: _.dictionary(obj:Object)

Given an object, returns a function that will attempt to look up a field that it is given.

var generals = {
    rome: "Scipio",
    carthage: "Hannibal"
};

var getGeneralOf = _.dictionary(generals);

getGeneralOf("rome");
// => "Scipio"

getPath

Signature: _.getPath(obj:Object, ks:String|Array)

Gets the value at any depth in a nested object based on the path described by the keys given. Keys may be given as an array or as a dot-separated string. Returns undefined if the path cannot be reached.

var countries = {
        greece: {
            athens: {
                playwright:  "Sophocles"
            }
        }
    }
};

_.getPath(countries, "greece.athens.playwright");
// => "Sophocles"

_.getPath(countries, "greece.sparta.playwright");
// => undefined

_.getPath(countries, ["greece", "athens", "playwright"]);
// => "Sophocles"

_.getPath(countries, ["greece", "sparta", "playwright"]);
// => undefined

hasPath

Signature: _.hasPath(obj:Object, ks:String|Array)

Returns a boolean indicating whether there is a property at the path described by the keys given. Keys may be given as an array or as a dot-separated string.

var countries = {
        greece: {
            athens: {
                playwright:  "Sophocles"
            }
        }
    }
};

_.hasPath(countries, "greece.athens.playwright");
// => true

_.hasPath(countries, "greece.sparta.playwright");
// => false

_.hasPath(countries, ["greece", "athens", "playwright"]);
// => true

_.hasPath(countries, ["greece", "sparta", "playwright"]);
// => false

kv

Signature: _.kv(obj:Object, key:String)

Returns the key/value pair for a given property in an object, undefined if not found.

var playAuthor = {
    "Medea": "Aeschylus"
};

_.kv(playAuthor, "Medea");
// => ["Medea", "Aeschylus"]

_.kv(playAuthor, "Hamlet");
// => undefined

omitWhen

Signature: _.omitWhen(obj, pred:Function)

Returns a copy of obj omitting any properties that the predicate (pred) function returns true for. The predicat function is invoked with each property value, like so: pred(propValue).

var playwrights = {
    euripedes: "Greece",
    shakespere: "England"
};

_.omitWhen(obj, function (country) { return country == "England" });
// => { euripedes: "Greece" }

pickWhen

Signature: _.pickWhen(obj:Object, pred:Function)

Returns a copy of obj containing only properties that the predicate (pred) function returns true for. The predicate function is invoked with each property value, like so: pred(propValue).

var playwrights = {
    euripedes: "Greece",
    shakespere: "England"
};

_.pickWhen(obj, function (country) { return country == "England" });
// => { shakespeare: "England" }

selectKeys

Signature: `_.selectKeys(obj:Object, ks:Array);

Returns a copy of obj containing only the properties listed in the ks array.

var philosopherCities = {
    Philo: "Alexandria",
    Plato: "Athens",
    Plotinus: "Rome"
}

_.selectKeys(philosopherCities, ["Plato", "Plotinus"]);
// => { Plato: "Athens", Plotinus: "Rome" }