JavaScript: Function Parameters
Number of Arguments Not Checked
JavaScript doesn't check the number of arguments passed in a function call.
- If there are more arguments passed in a function call than declared parameters, they are ignored.
- If less, then extra parameter variables have values of undefined .
function ff(x) { return x; } // extra arguments are ignored console.log(ff(2, 3, 4) === 2);
const gg = ((x) => x); // extra arguments are ignored console.log(gg(2, 3, 4) === 2);
// unfilled parameters have value of undefined function gg(x, y) { return y; } console.log(gg(3) === undefined);
// unfilled parameters have value of undefined const gg = ((x, y) => y); console.log(gg(3) === undefined);
Parameter Default Value
Rest Parameters
Function Argument Destructure
the γargumentsγ Object
How to find the number of arguments passed?
The total count of arguments passed is arguments.length
.
[see arguments Object]