Скачать или смотреть How to Create an Array of Arrays Filled with false in JavaScript

Discover how to efficiently create an array of arrays in JavaScript filled with the value `false` without running into common errors.
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This video is based on the question https://stackoverflow.com/q/66216335/ asked by the user 'scriptor6' ( https://stackoverflow.com/u/14953496/ ) and on the answer https://stackoverflow.com/a/66216447/ provided by the user 'Kosh' ( https://stackoverflow.com/u/5724303/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem

Creating a multi-dimensional array in JavaScript can be tricky, especially if you're trying to initialize it with specific values. If you're encountering unexpected errors when trying to build an array of arrays filled with false, you're not alone. Let's break down the issue.

The Error

You might find yourself facing the error:

[[See Video to Reveal this Text or Code Snippet]]

This typically occurs when you're trying to access an index of an array that hasn't been properly initialized yet. In the example code you provided:

[[See Video to Reveal this Text or Code Snippet]]

As you can see, while you're pushing an empty array into fieldFilled in the outer loop, you're incorrectly trying to push false into fieldFilled[j] in the nested loop. By doing this, you're referencing an index that doesn't exist yet because you haven't pushed any arrays corresponding to index j.

The Solution

To create a two-dimensional array filled with false, we'll utilize a more functional approach that avoids these common pitfalls. Here’s how you can do it:

Recommended Approach

Step 1: Create the Outer Array

You first need to create an array with a specified size (in this case, 10) filled with zeros (or any initial value).

Step 2: Using map to Create Inner Arrays

Utilize the map method to create inner arrays filled with false.

Here’s the code that achieves this:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

new Array(10): Creates a new array with 10 undefined elements.

.fill(0): Fills the outer array with zeros, just to initialize it.

.map(...): This function iterates over each element of the array (currently filled with zeros), replacing each zero with a new array.

new Array(10).fill(false): Each inner array is initialized at 10 elements all set to false.

Conclusion

By following the functional approach above, you can easily create an array of arrays filled with false in JavaScript without running into index-related errors. This method is not only cleaner but also more efficient and prevents common mistakes seen in nested loops.

With a clear understanding and the right code, you can now build and manipulate multi-dimensional arrays effortlessly in your JavaScript projects.