Variadic Functions ¶

Description ¶

When you want to declare a function with variable number of parameters in Python, you take advantage of the special *args syntax.

The JavaScript equivalent would be the rest parameter defined with the spread (…) operator :

           > function average(...numbers) {
   if (numbers.length > 0) {
     const sum = numbers.reduce((a, x) => a + x);
     return sum / numbers.length;
   }
   return 0;
}

          

           > average();
0
> average(1);
1
> average(1, 2);
1.5
> average(1, 2, 3);
2

          

The spread operator can also be used to combine iterable sequences.

For example, you can extract the elements of one array into another:

           const redFruits = ['apple', 'cherry'];
const fruits = ['banana', ...redFruits];

fruits

           Array(3) [ "banana", "apple", "cherry" ]

          

Depending on where you place the spread operator in the target list, you may prepend or append elements or insert them somewhere in the middle.