JS Bits with Bill
JS Bits with Bill

JS Bits with Bill

Easy console.log() inside one liner functions

Easy console.log() inside one liner functions

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JS Bits with Bill

Published on Nov 10, 2021

1 min read

Let's say we want to log obj inside this .map() function here:

const arr = [
  { val: 1 },
  { val: 2 },
  { val: 3 }
];

const nums = arr.map(obj => obj.val*2);

Well, dang! Now we have to convert this to a multi-line function, right?

const nums = arr.map(obj => {
  console.log(obj);
  return obj.val * 2;
});

Instead we can use the logical OR (||) operator with console.log() to short-circuit evaluate the return statement:

const nums = arr.map(obj => console.log(obj) || obj.val*2);

This works because console.log() evaluates to undefined so our OR (||) opertator will evalutate the next operand which is the return portion of the function and will return the same result as the original example!

This is especially usefull with JSX where we commonly render components with implicit return statements:

export default function App() {
  return (
    <div>
      <h2>Short-circuit Logging</h2>
      <ul>
        {nums.map((num) => console.log(num) || (
          <li key={num}>{num}</li>
        ))}
      </ul>
    </div>
  );
}

Huzzah! 😃


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