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Functional Programming Patterns With RamdaJS!

Inspecting With Tap

Explore how to use tap in RamdaJS to inspect values within function pipelines built with pipe and compose. Understand how tap aids debugging by allowing you to introduce logging or side effects without affecting the data stream, enhancing your ability to troubleshoot functional code.

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One of pipe's potential drawbacks is losing the ability to easily add code for debugging purposes.

Back when we had this

Javascript (babel-node)
const doMath = (num) => {
  const doubled = num * 2;
  const tripled = doubled * 3;
  const squared = tripled * tripled;
  return squared + 1;
}
const result = doMath(2);
console.log({ result });

Jamming a console.log or little hack was easy. How do we inspect piped functions?

Introducing tap. It takes a function, usually a logger, and supplies it the current value. You can do whatever you want without affecting the pipeline since you’re just “tapping” it! :D

Javascript (babel-node)
import { pipe, tap } from 'ramda';
const doMath = pipe(
  tap((num) => {
    console.log('initial number:', num);
  }),
  double,
  tap((num) => {
    console.log('after doubling:', num);
  }),
  triple,
  tap((num) => {
    console.log('after tripling:', num);
  }),
  
  square,
  tap((num) => {
    console.log('after squaring:', num);
  }),
  
  increment,
  tap((num) => {
    console.log('after incrementing:', num);
  }),
);
const result = doMath(2);
console.log({ result });

You don’t even need to use tap itself, just insert a function that returns its arguments unchanged.

Javascript (babel-node)
import { pipe, tap } from 'ramda';
const doMath = pipe(
  (num) => {
    console.log('initial number:', num);
    return num;
  },
  double,
  (num) => {
    console.log('after doubling:', num);
    return num;
  },
  triple,
  (num) => {
    console.log('after tripling:', num);
    return num;
  },
  
  square,
  (num) => {
    console.log('after squaring:', num);
    return num;
  },
  
  increment,
  (num) => {
    console.log('after incrementing:', num);
    return num;
  }
);
const result = doMath(2);
console.log({ result });