Rest operator: as parameter

Rest parameters in functions

must be the last parameter

const fn = (...rest, veryLast) => { assert.deepEqual(rest, [1, 2]); }; fn(1, 2);

can be used to get all other parameters

const fn = (firstParam, secondParam, rest) => { assert.deepEqual(rest, [3,4]); }; fn(null, 2, 3, 4);

makes arguments obsolete

const fn = () => { assert.deepEqual(args, [42, 'twenty three', 'win']); }; fn(42, 'twenty three', 'win');

eliminate arguments!!!

const fn = () => args; const [firstArg, ...rest] = fn(1, 2, 3); assert.deepEqual(rest, [2, 3]);

Related Katas

Unary Operators

• All unary operators
• Unary "+" operator
• Unary "+" operator in depth

Bitwise Shift Operators

• Left Shift "<<"
• Right Shift ">>"
• All bitwise shift operators

Rest operator

• as parameter
• with destructuring

Spread operator

• with arrays
• with strings

Difficulty Level

INTERMEDIATE

First Published

7 April 2015

Stats

4 tests to solve