Spread operator: with strings

Spread syntax with strings

expands each character of a string by prefixing it with ...

const [b, a] = [...'ab']; assert.equal(a, 'a'); assert.equal(b, 'b');

expands any kind of character

const arr = [...'12']; assert.deepEqual(arr, ['1', ' ', '☢', ' ', '2']);

works anywhere inside an array (must not be last)

const letters = ['a', 'bcd', 'e', 'f']; assert.equal(letters.length, 6);

don`t confuse with the rest operator

const [...rest] = ['1234', ...'5']; assert.deepEqual(rest, ['1', '2', '3', '4', '5']);

can also be used as function parameter

const max = Math.max('12345'); assert.deepEqual(max, 5);

Links

mdn docs Syntax docs on MDN.

Required Knowledge

• `const` declaration (Block scope)
• array (Destructuring)
• with destructuring (Rest operator)

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

13 April 2015

Stats

5 tests to solve