es6 · ES6 Basics

What is stored in the triangle array?

let point = [1,3], segment = [point,[5,5]], triangle = [...segment,[1,8]];

Answers

23
[1,3,5,5,1,8]
[ [1,3], [5,5], [1,8] ]

# Understanding JavaScript Array Storage and Spread Operator The correct answer to the quiz question is `[[1,3], [5,5], [1,8]]`. This is achieved by using JavaScript's spread operator and its method of storing array items. In JavaScript, an array can hold multiple values, and these values can be of any data type including other arrays. In this instance, we are dealing with multi-dimensional arrays. The variable `triangle` is defined as an array that includes two other arrays (`point` and an anonymous array `[5,5]`) and another anonymous array `[1,8]`. The spread operator (`...`) is used here to include the values of the `segment` array into the `triangle` array. However, it is important to note that the spread operator does not flatten the `segment` array, but it includes the arrays ("spread" them) as they are. Let's understand this with the given code: ```javascript let point = [1,3], segment = [point,[5,5]], triangle = [...segment,[1,8]]; ``` In this code: 1. `point` is an array with two elements `[1,3]`. 2. `segment` is an array with two elements, where each element itself is an array. The first element is `point` (`[1,3]`), and the second element is another array `[5,5]`. 3. `triangle` is defined using the spread operator (`...segment`) along with another array `[1,8]`. Because the spread operator simply "spreads" the `segment` array elements into the `triangle` array without flattening them, `triangle` ends up as being a multi-dimensional array (an array of arrays) as it includes all the constituent arrays of `segment` along with `[1,8]`. Hence, `triangle` is `[[1,3], [5,5], [1,8]]`. As a best practice, developers should keep a clear understanding of how JavaScript handles arrays and how the spread operator works with multi-dimensional arrays, to avoid any confusion or bugs that might arise. Understanding these concepts properly can also aid in writing more efficient and less error-prone code.