Missing Helper ‘__spreadArray’:Upgrading ‘tslib’ Required or This syntax requires an imported helper named ‘__spreadArray’ which does not exist in ‘tslib’. Consider upgrading your version of ‘tslib’.ts

 As the colors of Holi fade, I extend my warmest greetings to all. May you be blessed with good health and happiness in the days ahead.

Today, we’ll explore the purpose of the ‘__spread’ array and why it causes errors in TypeScript (while it works fine in JavaScript). I’ll provide an example to illustrate the issue and then share the solution I found while developing this feature in TypeScript.

Let’s start by discussing the purpose of the __spreadArray function.

The ‘__spreadArray’ helper function is used in TypeScript code that uses the spread operator (…) on an array. The spread operator is used to “spread” the elements of an array into a new array.

However, when using the spread operator with an empty array, it can sometimes cause issues in TypeScript. For example, consider the following code:

const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];

const combinedArr = […arr1, …arr2];

This code will work fine in JavaScript, but in TypeScript, it will produce an error,

error TS2532: Object is possibly ‘undefined’.

Now that we have a better understanding of the __spreadArray function, we can delve into the reasons why this error occurs specifically in TypeScript.

This error occurs because TypeScript is not sure if the arrays being spread are empty or not. To avoid this issue, the ‘__spreadArray’ helper function can be used instead of the spread operator when combining arrays. The ‘__spreadArray’ function takes two arguments: the first is the initial array, and the second is the array to be added.

Now, let’s move on to the solution. There are two ways to resolve this issue when working with TypeScript and Angular.

1. By importing __spreadArray in our .ts file: Here is an example of how ‘__spreadArray’ can be used to combine arrays safely in TypeScript:
   import { __spreadArray } from ‘tslib’;

const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];

const combinedArr = __spreadArray(__spreadArray([], arr1), arr2);

In this example, we use ‘__spreadArray’ to create a new array by first creating an empty array with ‘__spreadArray([], arr1)’, then adding ‘arr1’ to it, and finally adding ‘arr2’ to the result. The ‘__spreadArray’ function ensures that TypeScript understands that the first argument is an array and not undefined, which avoids the error that was produced earlier.

Now come to second solution.

2. By installing tslib library in our angular node module by following command.

npm install tslib@latest

Alternatively, if you are using a package manager other than npm, you can upgrade tslib using the appropriate command for your package manager.

Once you have upgraded tslib, you should no longer see this error message.

I hope you found this article informative and useful! If you know someone else who might be struggling with the same error, please share this article with them so they can benefit from this solution too. Thank you for reading!