CODESAMPLE

Composite - JavaScript

Composite JavaScript

The Composite pattern allows you to treat individual objects and compositions of objects uniformly. It’s used when you have a hierarchical structure where you need to perform operations on both individual elements and groups of elements. In this example, we model a file system where files and directories can both have a size() method. Directories contain other files/directories, representing the composite structure. The code uses JavaScript classes to define the component (File and Directory) and the composition (Directory). The consistent interface (size()) enables treating both files and directories interchangeably.

// Component interface
class FileSystemNode {
  constructor(name) {
    this.name = name;
  }

  size() {
    throw new Error("Method 'size()' must be implemented.");
  }
}

// Leaf node
class File extends FileSystemNode {
  constructor(name, fileSize) {
    super(name);
    this.fileSize = fileSize;
  }

  size() {
    return this.fileSize;
  }
}

// Composite node
class Directory extends FileSystemNode {
  constructor(name) {
    super(name);
    this.children = [];
  }

  add(node) {
    this.children.push(node);
  }

  size() {
    let totalSize = 0;
    for (const child of this.children) {
      totalSize += child.size();
    }
    return totalSize;
  }
}

// Example Usage
const root = new Directory("root");
const dir1 = new Directory("dir1");
const file1 = new File("file1.txt", 10);
const file2 = new File("file2.jpg", 100);

dir1.add(file1);
dir1.add(file2);
root.add(dir1);
root.add(new File("file3.pdf", 50));

console.log("Total size:", root.size()); // Output: Total size: 160