Avoiding Event Loop Blocking in JavaScript Applications

{
  "title": "Avoiding Event Loop Blocking in JavaScript Applications",
  "description": "Best practices for preventing event loop blocking to maintain responsive JavaScript applications.",
  "category": "JavaScript Cursor Rules",
  "rules": [
    {
      "id": "no-synchronous-io",
      "description": "Avoid using synchronous I/O operations to prevent blocking the event loop.",
      "severity": "error",
      "pattern": [
        {
          "type": "CallExpression",
          "callee": {
            "type": "MemberExpression",
            "object": {
              "type": "Identifier",
              "name": "fs"
            },
            "property": {
              "type": "Identifier",
              "name": "readFileSync"
            }
          }
        },
        {
          "type": "CallExpression",
          "callee": {
            "type": "MemberExpression",
            "object": {
              "type": "Identifier",
              "name": "fs"
            },
            "property": {
              "type": "Identifier",
              "name": "writeFileSync"
            }
          }
        },
        {
          "type": "CallExpression",
          "callee": {
            "type": "MemberExpression",
            "object": {
              "type": "Identifier",
              "name": "fs"
            },
            "property": {
              "type": "Identifier",
              "name": "appendFileSync"
            }
          }
        },
        {
          "type": "CallExpression",
          "callee": {
            "type": "MemberExpression",
            "object": {
              "type": "Identifier",
              "name": "fs"
            },
            "property": {
              "type": "Identifier",
              "name": "unlinkSync"
            }
          }
        }
      ],
      "message": "Use asynchronous file system methods instead of synchronous ones to avoid blocking the event loop."
    },
    {
      "id": "no-blocking-loops",
      "description": "Avoid long-running synchronous loops that can block the event loop.",
      "severity": "error",
      "pattern": [
        {
          "type": "WhileStatement",
          "test": {
            "type": "Literal",
            "value": true
          }
        },
        {
          "type": "ForStatement",
          "test": {
            "type": "Literal",
            "value": true
          }
        }
      ],
      "message": "Refactor long-running loops to use asynchronous techniques like setTimeout or process.nextTick to prevent blocking the event loop."
    },
    {
      "id": "no-heavy-computation",
      "description": "Offload heavy computations to prevent blocking the event loop.",
      "severity": "error",
      "pattern": [
        {
          "type": "CallExpression",
          "callee": {
            "type": "Identifier",
            "name": "computePrimes"
          }
        },
        {
          "type": "CallExpression",
          "callee": {
            "type": "Identifier",
            "name": "calculateFibonacci"
          }
        }
      ],
      "message": "Consider using Web Workers or child processes to handle CPU-intensive tasks without blocking the event loop."
    },
    {
      "id": "no-unoptimized-regex",
      "description": "Avoid using inefficient regular expressions that can cause event loop blocking.",
      "severity": "error",
      "pattern": [
        {
          "type": "Literal",
          "value": "/(\\/.*)+$/"
        }
      ],
      "message": "Optimize regular expressions to prevent performance issues and potential event loop blocking."
    },
    {
      "id": "no-large-json-operations",
      "description": "Avoid processing large JSON objects synchronously to prevent blocking the event loop.",
      "severity": "error",
      "pattern": [
        {
          "type": "CallExpression",
          "callee": {
            "type": "Identifier",
            "name": "JSON.parse"
          },
          "arguments": [
            {
              "type": "Identifier",
              "name": "largeJsonString"
            }
          ]
        },
        {
          "type": "CallExpression",
          "callee": {
            "type": "Identifier",
            "name": "JSON.stringify"
          },
          "arguments": [
            {
              "type": "Identifier",
              "name": "largeJsonObject"
            }
          ]
        }
      ],
      "message": "Use streaming parsers or chunk processing for large JSON data to avoid blocking the event loop."
    }
  ]
}