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composeRight

TS JS Deno

Performs left-to-right function composition.

Use Array.prototype.reduce() to perform left-to-right function composition. The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.

typescript
const composeRight = (...fns) =>
  fns.reduce(
    (f, g) =>
      (...args) =>
        g(f(...args))
  );
typescript
const multiply = (x: number, y: number) => x * y;
const add5 = (x: number) => x + 5;
const multiplyAndAdd5 = compose(multiply, add5);
multiplyAndAdd5(5, 2); // 15

Complex Example- Return with tuple:

typescript
const multiply = (x: number, y: number) => x * y; // 5* 2 = 10
const add3 = (x: number) => [x + 3, 3]; // [10+3, 3] = [13, 3]
const add = (x: number, y: number) => x + y; // 13 + 3 = 16
const multiplyAndAdd3 = composeRight(multiply, add3, add);
assertEquals(multiplyAndAdd3(5, 2), 16);