SyntaxError: rest parameter may not have a default
The JavaScript exception "rest parameter may not have a default" occurs when arest parameter has adefault value. Because the rest parameter always creates an array, the default value would never apply.
Message
SyntaxError: Rest parameter may not have a default initializer (V8-based)SyntaxError: rest parameter may not have a default (Firefox)SyntaxError: Unexpected token '='. Expected a ')' or a ',' after a parameter declaration. (Safari)
Error type
What went wrong?
Adefault parameter gives a parameter a default value if the argument is not passed or passed asundefined. Arest parameter collects all the remaining arguments passed to the function and always creates an array. Therefore, it doesn't make sense to have a default value for a rest parameter.
Examples
Invalid cases
js
function doSomething(...args = []) {}Valid cases
js
function doSomething(...args) { // args is always an array}