graphHasEdge.js

class graph{
    constructor(){
        this.adjacenyList={}
    }

    addVertex(vertex){
        if(!this.adjacenyList[vertex]){
            this.adjacenyList[vertex]= new Set()
        }
    }

    addEdge(vertex1,vertex2){
        if(!this.addVertex[vertex1]){
            this.addVertex(vertex1)
        }
        if(!this.addVertex[vertex2]){
            this.addVertex(vertex2)
        }
        this.adjacenyList[vertex1].add(vertex2)
        this.adjacenyList[vertex2].add(vertex1)
    }

    display(){
        for(let vertex in this.adjacenyList){
            console.log(vertex + "->"+ [...this.adjacenyList[vertex]]);
        }
    }

    hasEdge(vertex1,vertex2){
        return(
            this.adjacenyList[vertex1].has(vertex2)&&
            this.adjacenyList[vertex2].has(vertex1)
        )
    }
}

let gr=new graph()
gr.addVertex("A")
gr.addVertex("B")
gr.addVertex("C")

gr.addEdge("A","B")
gr.addEdge("B","C")

gr.display()

console.log(gr.hasEdge("A","B"));