I'm new to javascript, thus the question. I've the following object,
class Node{ constructor(data){ this.data = data; this.adjacencySet = new Set(); } addEdge(node){ this.adjacencySet.add(node) } getAdjacentVertices(){ return this.adjacencySet; } } How do I check the presence of this object in a hash map. An analogy would be in Python I'd add the following method in the class,
def __eq__(self, other): return this.data == other.data How can do a similar object comparison in javascript?
What do you mean by hashmap in javascript? There is no such collection here.
Anyways, Equality depends on what the data is.
If its a value type (boolean, string, number), then you simply compare then via === or == operator. Where the later operator automatically convert either or both the sides (LHS/RHS) of the equation to make them the same type, so the following would suffice:
this.data === other.data; // value comparison; e.g: 1 === 3; is false If its a reference type(array, object) then comparing both objects would result in a memory address check, where if they are different then it would result in false. If you would want to compare their values then you would have to iterate the index (for array) or keys (for object) in order to check for equality.
this.data === other.data; // reference comparison; this.data = [1,2,3] (memory = 1234), other.data = [1,2,3] (memory = 1235); is false 
Map and Set data structures in JavaScript.
data value, we don't know what data type is data, so therefore telling him how equality works behind the scene, he may get a hint on how to set the equality of his data structure.
==object comparison in JavaScript is always based on the actual identity of the objects. Two different objects are never==no matter how similar they are.MaporSet, which I think is what the OP wanted to achieve.