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JavaScript JavaScript Array Iteration Methods Combining Array Methods Nested Data and Additional Exploration

Posted by vincenzo IEVA
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vincenzo IEVA
Front End Web Development Techdegree Graduate 14,211 Points

spread operator in this case

Hi,

can someone help me understand what the spread operator does in this case? [...arr, ...innerMovies]

thanks

Andrey Misikhin
Andrey Misikhin
16,529 Points
Andrey Misikhin
Andrey Misikhin
16,529 Points

It is concatenation of two arrays. For example, 

let arr = [1, 2, 3];
let innerMovies = ['a', 'b', 'c'];
let result = [...arr, ...innerMovies];
console.log(result);

If you will do it, than you will see, that you received a new array, that consists of previous two.

[1, 2, 3, 'a', 'b', 'c']

1 Answer

Steven Parker
Steven Parker
229,670 Points
Steven Parker
Steven Parker
229,670 Points

What the spread operator itself does is to convert a collection of items into its individual elements. In your example, "arr" is an array with potentially several elements; and "...arr" is the elements all listed out as separate items.

This lets you do things in one step that would otherwise require loops, such as your example of re-combining multiple arrays into a single one.