Builder Design Pattern with Typescript

designpatterns-builder.ts

interface QueryBuilder {
  table(table): QueryBuilder;
  select(cols): QueryBuilder;
  limit(value: Number): QueryBuilder;
  where(col, value): QueryBuilder;
  getQuery(): String;
  
  /* +100 Other SQL Methods  */
}

class MySqlQueryBuilder implements QueryBuilder {
  private query: String;
  private tableName: String;

  public constructor() {
    this.query = '';
  }

  public table(table): QueryBuilder {
    this.tableName = table;

    return this;
  }

  public select(cols): QueryBuilder {
    /** ... */
    return this;
  }

  public limit(value: Number): QueryBuilder {
    /** ... */
    return this;
  }
  
  public where(col, value): QueryBuilder {
    /** ... */
    return this;
  }

  public getQuery(): String {
    return 'This is a MySQL query';
  }
}

class MongoDbQueryBuilder implements QueryBuilder {
  private query: String;
  private tableName: String;

  public constructor() {
    this.query = '';
  }

  public table(table): QueryBuilder {
    this.tableName = table;

    return this;
  }

  public select(cols): QueryBuilder {
    /** ... */
    return this;
  }

  public limit(value: Number): QueryBuilder {
    /** ... */
    return this;
  }
  
  public where(col, value): QueryBuilder {
    /** ... */
    return this;
  }

  public getQuery(): String {
    return 'This is a MongoDB query';
  }
}







function client(builder: QueryBuilder) {
  const query = builder.table('posts').where('id', 429).limit(10).select(['id', 'title']).getQuery();

  console.log(query);
}


const config = {
  database1: MongoDbQueryBuilder,
  database2: MySqlQueryBuilder
}

client(new config.database1); // This is a MongoDB query
client(new config.database2); // This is a MySQL query