Function.lenght will tell you the number of the required arguments for a Javascript function

DanielMay 14, 2021May 17, 2021

Just found out that any javascript function has a lenght property. It will return how many arguments are mandatory for that function:

const myFunction = (a, b, c) => {}
console.log(myFunction.length) // 3

Of course that if we provide a default value for an argument it will not be considered mandatory:

const myFunction = (a, b, c = 'some value') => {}
console.log(myFunction.length) // 2

Also, using the spread syntax will not count as a mandatory parameter.

const myFunction = ( operation, ...numbers ) => {}
console.log(myFunction.length) // 1

Not sure how useful this is daily but it’s a fun trick to know. Javascript … the forever surprising language 😀