trekhleb/javascript-algorithms · error · Error

Edge not found in graph

Error message

Edge not found in graph

What it means

Graph.deleteEdge() removes the entry under edge.getKey() from this.edges and throws at Graph.js:103-107 when that key is absent - deleting an edge the graph does not hold is treated as a bug, not a no-op. It then also strips the edge from both endpoint vertices. Because keys are direction-sensitive ('start_end'), an edge can be missing even when the reverse pair exists in an undirected graph.

Source

Thrown at src/data-structures/graph/Graph.js:106

      startVertex.addEdge(edge);
    } else {
      // If graph ISN'T directed then add the edge to both vertices.
      startVertex.addEdge(edge);
      endVertex.addEdge(edge);
    }

    return this;
  }

  /**
   * @param {GraphEdge} edge
   */
  deleteEdge(edge) {
    // Delete edge from the list of edges.
    if (this.edges[edge.getKey()]) {
      delete this.edges[edge.getKey()];
    } else {
      throw new Error('Edge not found in graph');
    }

    // Try to find and end start vertices and delete edge from them.
    const startVertex = this.getVertexByKey(edge.startVertex.getKey());
    const endVertex = this.getVertexByKey(edge.endVertex.getKey());

    startVertex.deleteEdge(edge);
    endVertex.deleteEdge(edge);
  }

  /**
   * @param {GraphVertex} startVertex
   * @param {GraphVertex} endVertex
   * @return {(GraphEdge|null)}
   */
  findEdge(startVertex, endVertex) {
    const vertex = this.getVertexByKey(startVertex.getKey());

View on GitHub (pinned to 85293e3e2b)

Solutions

1. Fetch the stored edge and delete that instance: const stored = graph.findEdge(u, v); if (stored) graph.deleteEdge(stored); - findEdge() matches both orientations.
2. Guard by key: if (graph.edges[edge.getKey()]) graph.deleteEdge(edge);
3. Delete in a single pass over graph.getAllEdges() and do not re-enqueue deletions.
4. Normalize endpoint order for undirected graphs before constructing the edge you delete.

Example fix

// before
graph.deleteEdge(edge);
graph.deleteEdge(edge); // Error: Edge not found in graph

// after
const stored = graph.findEdge(edge.startVertex, edge.endVertex);
if (stored) {
  graph.deleteEdge(stored);
}

// findEdge() resolves either orientation and returns the stored instance
const stored = graph.findEdge(startVertex, endVertex);
if (stored) {
  graph.deleteEdge(stored);
}

try {
  graph.deleteEdge(edge);
} catch (error) {
  if (error.message === 'Edge not found in graph') {
    // already deleted or never added - treat as an idempotent no-op
  } else {
    throw error;
  }
}

When it happens

Trigger: Calling deleteEdge(edge) twice (the first call removes the key); deleting an edge that was never added; constructing new GraphEdge(b, a) to delete an undirected edge that was stored under the a_b key; deleting after edge.reverse() or after endpoint mutation changed getKey().

Common situations: Cleanup loops that visit the same edge twice (iterating a copied edge list while queueing deletions); mixed endpoint ordering between the add path and the delete path; tests that delete fixture edges repeatedly without rebuilding the graph.

Related errors

• One or two values are not in sets
• Vertex has already been added before
• Edge has already been added before
• Graph vertex must have a value

AI-assisted analysis of trekhleb/javascript-algorithms@85293e3e2b (2026-08-24). Data as JSON: /api/errors/afaf6d7b30a8a9b7. Report an issue: GitHub.