krahets/hello-algo · error · RangeError

Index Out Of Bounds Exception

Error message

Index Out Of Bounds Exception

What it means

Thrown as a RangeError by removeVertex(index) on an adjacency-matrix graph when index >= size() (the number of vertices). Note the guard checks only the upper bound (index >= size) and omits the negative-index check, but the subsequent splice with a negative index would behave unexpectedly. It removes the vertex's row/column from the matrix.

Source

Thrown at en/codes/javascript/chapter_graph/graph_adjacency_matrix.js:52

        const n = this.size();
        // Add the value of the new vertex to the vertex list
        this.vertices.push(val);
        // Add a row to the adjacency matrix
        const newRow = [];
        for (let j = 0; j < n; j++) {
            newRow.push(0);
        }
        this.adjMat.push(newRow);
        // Add a column to the adjacency matrix
        for (const row of this.adjMat) {
            row.push(0);
        }
    }

    /* Remove vertex */
    removeVertex(index) {
        if (index >= this.size()) {
            throw new RangeError('Index Out Of Bounds Exception');
        }
        // Remove the vertex at index from the vertex list
        this.vertices.splice(index, 1);

        // Remove the row at index from the adjacency matrix
        this.adjMat.splice(index, 1);
        // Remove the column at index from the adjacency matrix
        for (const row of this.adjMat) {
            row.splice(index, 1);
        }
    }

    /* Add edge */
    // Parameters i, j correspond to the vertices element indices
    addEdge(i, j) {
        // Handle index out of bounds and equality
        if (i < 0 || j < 0 || i >= this.size() || j >= this.size() || i === j) {
            throw new RangeError('Index Out Of Bounds Exception');

View on GitHub (pinned to 69932aed18)

Solutions

1. Guard the call: if (index >= 0 && index < graph.size()) graph.removeVertex(index);
2. Re-resolve indices from labels immediately before removal rather than caching them.
3. If removing multiple vertices by index, do so from highest to lowest to keep earlier indices stable.
4. Confirm you are passing a numeric index, not a vertex label object.

Example fix

// before
graph.removeVertex(index); // index may be >= size() -> throws

// after
if (index >= 0 && index < graph.size()) {
  graph.removeVertex(index);
}

function canRemoveVertexIndex(graph, index) {
  return Number.isInteger(index) && index >= 0 && index < graph.size();
}
if (canRemoveVertexIndex(graph, i)) graph.removeVertex(i);

function isValidVertexIndex(graph, index) {
  return typeof index === 'number' && Number.isInteger(index) && index >= 0 && index < graph.size();
}

try {
  graph.removeVertex(i);
} catch (e) {
  if (e instanceof RangeError) { /* out of range */ }
  else throw e;
}

When it happens

Trigger: Calling removeVertex(index) with index >= graph.size(), or with a negative index (not explicitly guarded, may cause splice quirks rather than a clean throw). After removals, a previously valid index can become out of range.

Common situations: Using a cached vertex count/index after prior removeVertex calls shrank the matrix; off-by-one when mapping a label to an index; passing the vertex label instead of its numeric index; forgetting that indices shift after deletion.

Related errors

• Index Out Of Bounds Exception
• Index Out Of Bounds Exception
• Index Out Of Bounds Exception
• 顶点索引越界
• 边索引越界或相等

AI-assisted analysis of krahets/hello-algo@69932aed18 (2026-08-13). Data as JSON: /api/errors/988f88ef511a9876. Report an issue: GitHub.