What is function composition in JavaScript?
Chaining small functions into a pipeline. compose(f, g) returns a function that does f(g(x)). This lets you build complex behavior from simple, reusable functions. It relies on functions being first-class (passable and returnable).
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More FAQs in Functions as Arguments and Return Values in JavaScript
Yes. This is a callback. setTimeout, map, filter, reduce, event listeners, and fetch.then all accept functions as arguments. The receiving function (higher-order) calls the callback at the right time.
Yes. A function that returns another function is a higher-order function (a function factory). The returned function often closes over the outer function's variables, creating a closure.
A function that takes a function as an argument, returns a function, or both. Examples: map, filter, reduce, compose, curry, partial, setTimeout, and event listeners.
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