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Update /content/lessons/typescript-design-patterns/index.md #1670

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16 changes: 8 additions & 8 deletions content/lessons/typescript-design-patterns/index.md
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Expand Up @@ -20,7 +20,7 @@ youtube: tv-_1er1mWI
# rxdart: 0.20
---

[Design patterns](https://en.wikipedia.org/wiki/Design_Patterns) is a highly influential book published in 1994 by four computer scientists called the *Gang of Four*. It was originally aimed at C++ developers, but has since become a book for anyone interested in object-oriented software design.
[Design Patterns](https://en.wikipedia.org/wiki/Design_Patterns) is a highly influential book published in 1994 by four computer scientists called the *Gang of Four*. It was originally aimed at C++ developers, but has since become a book for anyone interested in object-oriented software design.

In the following lesson, we will look at 10 different patterns from this book with simplified modern examples in TypeScript. For additional patterns and examples, check out [Refactoring Guru](https://refactoring.guru).

Expand All @@ -30,7 +30,7 @@ Creational patterns are related to the creation of new objects.

### Singleton

A singleton is an object that can only be instantiated once. It is useful fo implementing a global object that can be accessed from anywhere in the application.
A singleton is an object that can only be instantiated once. It is useful for implementing a global object that can be accessed from anywhere in the application.

{{< file "ts" "software.ts" >}}
```typescript
Expand Down Expand Up @@ -60,7 +60,7 @@ const settings = Settings.getInstance();

### Prototype

Prototype allows objects to be clones of other objects, rather then extended via inheritance.
Prototype allows objects to be clones of other objects, rather than extended via inheritance.

{{< file "ts" "software.ts" >}}
```typescript
Expand Down Expand Up @@ -109,7 +109,7 @@ const btn2 = factory.createButton(os);
```
### Builder

The builder pattern is a creational design pattern that lets you construct complex objects step by step. It JavaScript, we can achieve this with method chaining.
The builder pattern is a creational design pattern that lets you construct complex objects step by step. In JavaScript, we can achieve this with method chaining.

{{< file "ts" "software.ts" >}}
```typescript
Expand Down Expand Up @@ -146,7 +146,7 @@ Structural patterns are primarily used to handle relationships between objects.

### Facade

A facade is a class that provides a simplified API for larger body of code. It is often to used to hide low-level details of a subsystem.
A facade is a class that provides a simplified API for a larger body of code. It is often to used to hide low-level details of a subsystem.

{{< file "ts" "software.ts" >}}
```typescript
Expand Down Expand Up @@ -217,7 +217,7 @@ Behavioral patterns are used to identify communication between objects.

### Iterator

The iterator pattern is used to traverse a collection of elements. Most programming languages provide abstrations for iteration like the `for` loop. However, you can create your own iterators in JavaScript by using the `Symbol.iterator` property. The code below creates a custom range function that can be used in a regular `for` loop.
The iterator pattern is used to traverse a collection of elements. Most programming languages provide abstractions for iteration like the `for` loop. However, you can create your own iterators in JavaScript by using the `Symbol.iterator` property. The code below creates a custom range function that can be used in a regular `for` loop.

{{< file "ts" "software.ts" >}}
```typescript
Expand All @@ -243,7 +243,7 @@ for (const n of range(0, 100, 5)) {
```
### Observer

The observer pattern is used to notify a set of interested parties when a state change occurs. The [rxjs]() library is a popular implementation of this pattern.
The observer pattern is used to notify a set of interested parties when a state change occurs. The [rxjs](https://rxjs.dev/guide/overview) library is a popular implementation of this pattern.

{{< file "ts" "software.ts" >}}
```typescript
Expand All @@ -262,7 +262,7 @@ tv1.unsubscribe();
```
### Mediator

The mediator is provids a middle layer between objects that communicate with each other. This pattern implemented frequently in JavaScript libaries via plugin systems (like Webpack) and middleware (like Express).
The mediator pattern provides a middle layer between objects that communicate with each other. This pattern is implemented frequently in JavaScript libaries via plugin systems (like [Webpack](https://webpack.js.org)) and middleware (like [Express](https://expressjs.com/en/resources/middleware.html)).

{{< file "ts" "software.ts" >}}
```typescript
Expand Down