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Understanding Javascript Array Series II - Alternate ways of Creating an Array.

Nedy Udombat on September 30, 2019

In the first part of this series, I talked about what an array is and how to create an array here. Underst...

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Ameet Kaustav • Oct 1 '19 • Edited

Great article, @Nedy. Helped me understand the origins of some RxJS methods now. See RxJS.of and RxJS.from.

Found an issue though, which you might want to fix:

const arr3 = Array.from([1, 'nedy', undefined, null]);
// Seems to output [1, "nedy", undefined, null]
// instead of ["n", "e", "d", "y"]

Nedy Udombat • Oct 1 '19

Thanks a lot @akaustav , this must have been an oversight. I appreciate.

Benon Kityo • Oct 1 '19

Hi Nedy,thanks for the great article. Am a novice who is struggling with functions and would appreciate your help.
Var Repository =[
{
name:'Butterfree',
height:1.1,
types:['bug','flying']
},
{
name:'pidgey',
height:0.3,
types:['flying','normal']
},
{
name:'metapod',
height:0.5,
types:['bug']
}
];
repository.forEach(function(repository){
Please help me to write this repo using document.write

Seanmclem • Oct 1 '19

Hey thanks. Just used array.fill and it worked perfectly

Nedy Udombat • Oct 1 '19

I am glad you found this useful, This has made my day @seanmclem .

Abdulkareem Mustopha • Oct 1 '19

A newbie is confused...
Why is array().fill and array.of returning undefined for numbers?

Nedy Udombat • Oct 1 '19

Hi @aphatheology Array.fill() takes three arguments.

The first argument is the value you want to fill the array with, it can range from a string to an number to to even another array.

The second argument is the index of the array in which you want to start filling the array from. If you do this Array(5).fill(3, 2). This means you want to fill the array from index 2 till the end with the value if 3. This will return [undefined, undefined, 3, 3, 3]

The third argument is the index position of the array in which you want to stop filling the array. Array(5).fill(3, 2, 4) will give you this [undefined, undefined, 3, 3, undefined].

Array.of() doesn't return undefined for numbers.