How to use thisArg in Lo-Dash?

Question

How do I use the thisArg in Lo-Dash? Is it possible to combine it with chaining? This is an example that uses thisArg from their documentation:

_.map(collection, [callback=identity], [thisArg])

Creates an array of values by running each element in the collection through the callback. The callback is bound to thisArg and invoked with three arguments; (value, index|key, collection).

If a property name is provided for callback the created "_.pluck" style callback will return the property value of the given element.

If an object is provided for callback the created "_.where" style callback will return true for elements that have the properties of the given object, else false.

Aliases

_.collect

Arguments

collection (Array|Object|string): The collection to iterate over.
[callback=identity] (Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.
[thisArg] (*): The this binding of callback.
Returns

(Array): Returns a new array of the results of each callback execution.

An example would be appreciated, as I wasn't able to find any in their documentation.

Answer 1

Argument thisArg is just a pointer to this context of the caller that will also be used as the context of callback. It is provided for convenience.

The result is the same as if using native Function.bind() method e.g.:

_.map(collection, callback.bind(this));

An alternative approach would be to make an alias variable of this and use it instead.