We defined them as functions that take other functions as arguments &&/|| return new or modified functions. The intention of these is to make an abstraction of what happens inside. They are 'higher-order' because thay intend to resume what they do in its inside with its name without having to understand strictly with the code in its inside so that the programmer can be more concentrated on the inout/output or specific task that the higher order function does. Programs are often very complex and the engineer cant be aware of every single bit of code that runs within it.
Higher order functions are oftenly used to analyze sets of data stored in objects and arrays
filter method
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This means to store elements from an array that have certain property/s. The author explains how the 'filter' array method works in its inside but it is defined already by default...
it works like this:
array.filter(function)
map method
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The map method takes an array of objects and returns just a part of each object.
reduce method
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It intends to summarize information from a data set.