Eloquent JavaScript

Other Functional Tricks

Before moving on to the next chapter, I would like to show you a few more functional techniques that can, once you’ve gotten used to them, make your programs more succinct.

Operator Functions

When using higher-order functions, it is often annoying that operators are not functions in JavaScript. For example, we had to define the add function earlier in this chapter. Writing these out every time we need them is a pain. One way to get around that is to create an object like this:

var op = {
  "+": function(a, b){return a + b;},
  "==": function(a, b){return a == b;},
  "===": function(a, b){return a === b;},
  "!": function(a){return !a;}
  /* and so on */
};

So, we can write reduce(op["+"], 0, [1, 2, 3, 4, 5]) to sum an array.

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