Array API: array.entries()

[].entries() returns an iterator object with all entries

returns key+value for each element

const arr = ['a', 'b', 'c']; const entriesAsArray = Array.from(arr.___()); assert.deepEqual(entriesAsArray, [[0,"a"], [1,"b"], [2,"c"]]);

empty elements contain the value undefined

const arr = ['one']; arr[2] = 'three'; const secondValue = arr.entries(); assert.deepEqual(secondValue, [1, void 0]);

returns an iterable

has next() to iterate

const arr = ['one']; const value = arr; assert.deepEqual(value, [0, 'one']);

Required Knowledge

• `const` declaration (Block scope)
• `Array.from()` (Array API)
• protocol (Iterator)

Related Katas

Array API

• array.sort() basics
• array.sort() can take a compare function
• array.shift() (as introduced in ES3)
• array.push() (as introduced in ES3)
• Array.from()
• Array.of()
• array.fill()
• array.find()
• array.findIndex()
• array.entries()
• array.keys()
• array.values()
• array.includes()
• array.toReversed()

Difficulty Level

INTERMEDIATE

First Published

18 May 2015

Stats

3 tests to solve