Data structures.

graph.js

class Graph {
  
  adjList = new Map()
  
  constructor(iterable, directed = true){
    for(let node of iterable){
      this.adjList.set(node, new Map());
    }
  }
  
  adjacent(x, y){
    if(this.adjList.has(x)){
      if(this.adjList.get(x).has(y)){
        if(this.asjList.get(x).get(y).size > 0){
          return true;
        }
      }
    }
    return false
  }
  
  neighbours(x){
    if(this.adjList.get(x)){
      return new Set([for ([node] of this.adjList.get(x)) node]);
    }
    return new Set([]);
  }
  
  * edges(){
    const done = new Set();
    for(let [, value] of this.adjList){
      for(let [, edges] of value){
        for(let edge of edges){
          if(!done.has(edge)){
            done.add(edge);
            yield edge;
          } 
        }
      }
    }
  }
  
  * nodes(){
    for(let [key] of this.adjList){
      yield key;
    }
  }
  
  addEdge(to, from, edge){
    if(this.adjList.has(to)){
      if(!this.adjList.get(to).has(from)){
        this.adjList.get(to).set(from, new Set())
      }
      this.adjList.get(to).get(from).add(edge);
      if(!this.directed){
        if(!this.adjList.get(from).has(to)){
          this.adjList.get(from).set(to, new Set())
        }
        this.adjList.get(from).get(to).add(edge);
      } 
    }
    return this;
  }
  
  addNode(node){
    if(!this.adjList.has(node)){
      this.adjList.set(node, new Map());
    }
    return this;
  }
  
  getEdges(to, from){
    if(this.adjList.has(to)){
      if(this.adjList.get(to).has(from)){
        new Set(this.adjList.get(to).get(from));
      }
    }
    return new Set([]);
  }
  
  removeEdge(to, from, edge){
    if(this.adjList.has(to)){
      if(this.adjList.get(to).has(from)){
        this.asjList.get(to).get(from).remove(edge);
      }
    }
    return this;
  }
  
  removeNode(node){
    this.adjList.delete(node);
    for (let [key] of this.adjList){
      this.adjList.get(key).delete(node);
    }
    return this;
  }
  
  * [Symbol.iterator](){
    for(let [key] of this.adjList){
      yield key;
    }
  }
  
  get [Symbol.toStringTag](){
    return "Graph";
  }
  
}