Currying and partial application in JavaScript

Fixing some arguments now and the rest later.

const scale = (factor) => (value) => value * factor;
const double = scale(2);

console.log(double(21), [1, 2, 3].map(scale(10)));

function format(prefix, unit, value) {
  return `${prefix}${value}${unit}`;
}

const asPercent = format.bind(null, "", "%");
console.log(asPercent(97.5));

const curry3 = (fn) => (a) => (b) => (c) => fn(a, b, c);
console.log(curry3(format)("~")("tpm")(104));

How it works

A curried function takes one argument and returns a function.
bind does partial application, and also fixes this.
Argument order decides how reusable the partial is.

Keywords and builtins used here

const
double
function
return

The run, in numbers

Lines: 14
Characters to type: 387
Tokens: 144
Three-star pace: 105 tpm

At the three-star pace of 105 tokens a minute, this run takes about 82 seconds.

Type this snippet

Step 2 of 5 in Composing functions, step 6 of 16 in Functions & patterns.

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