Constraining Generic Types with Examples

// This class takes an array of strings or numbers and concatenates them into a single string
class Concatenator<T extends Array<string> | Array<number>> {
  
  // Method that concatenates the array of items into a string
  public concatenateArray(items: T): string {
    
    // Initialize an empty string to store the concatenated values
    let returnString = "";
    // Loop through each item in the array
    for (let i = 0; i < items.length; i++) {
      // If this is not the first item, add a comma before appending the value
      returnString += i > 0 ? "," : "";
      
      // Append the current value to the return string
      returnString += items[i].toString();
    }
    // Return the final concatenated string
    return returnString;
  }
}