JavaScript function default parameters

Question

const add = (a = 1, b = 1, c = 1) => a + b + c
add(4, , 2)

Throws Uncaught SyntaxError, unexpected token ','

How do I call the function so b defaults to the value 1

Answer 1

Just take undefined as value.

const add = (a = 1, b = 1, c = 1) => a + b + c
console.log(add(4, undefined, 2));

Answer 2

Pass undefined as value

Check this: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters#passing_undefined_vs._other_falsy_values

const add = (a = 1, b = 1, c = 1) => a + b + c
console.log(add(4, undefined, 2))