Arrow functions with implicit returns are an awesome, concise way to interact with data.
An example of an arrow function with implicit return
const sum = (a, b) => a + b;
Where an arrow function without an implicit return would look like this:
const sum = (a, b) => { return a + b; }
Very similar but in the first example, the return value of the function is inferred where in the latter, we're specifying the return statement of the function.
Logging in a standard function / arrow function is pretty straight-forward
const sum = (a, b) => {
console.log('HERE!');
return a + b;
}
But how do we accomplish this same thing in an arrow function with implicit return? Many times, developers convert the function with implicit return to a standard function but this isn't necessary.
A potential solution
We can take advantage of the fact that console.log is evaluated as falsy. This means that if we ran
if(console.log('someStatement')) {
// ...
} else {
...
}
We would encounter our else block every time. Using this knowledge, we can now update our arrow function with logging as follows:
const sum = (a, b) => console.log('A:', a, 'B:', b) || a + b;
Top comments (11)
Really nice!
And also, using an object into
console.logprints both the variable name and its value, like:console.log({a, b})Thank you! This is a really great point!
Ryan just informed me that TypeScript knows console.log is void function so you need to cast it to any.
Thanks again.
That's wicked smart
Great tip Ryan!
That's super clever! I log in functions like this all the time, but I add braces and convert to an explicit return
Thats nice share
Any suggestions on getting this approach to work in TS?
Very helpful but why does console.log evaluate to falsy and why does it still log when false?
really helpful
For Typescript, I think this is easier (a,b) => (console.log(a), a+b)
The comma will only return the last expression-