eslint-plugin-console-time-pairs

Ensure console.timeEnd is called for each console.time.

Why?

Finding out at runtime that you've typoed a label, or forgot to call time or timeEnd is not fun. This plugin makes sure every call to time has a matching call to timeEnd (and vice versa) so you can catch those mistakes at lint-time instead of run-time.

function() {
  console.time("Some long operation");
  // ...
  console.timeEnd("Some looong operation"); // Generates a warning!
}

Installation

# npm
npm install eslint-plugin-console-time-pairs --save-dev
# yarn
yarn add eslint-plugin-console-time-pairs --dev

In your .estlintrc.js add "console-time-pairs" to the plugin list.

plugins: [
  "console-time-pairs",
],

Then in the rules section set "console-time-pairs/console-time-pairs" pass the log level (either "error" or "warning").

rules: {
  "console-time-pairs/console-time-pairs": "error",
},

Configuration (Optional)

Object names

By default only console.time and console.timeEnd will be scanned. To also scan calls like logger.time specify "logger" in the objectNames array.

rules: {
  "console-time-pairs/console-time-pairs": ["error", {
    "objectNames": ["console", "logger", "myCustomTimerUtil"],
  }],
},

Scope

By default the entire file will be checked for matching time/timeEnd calls. But this behavior can be customized with the scope option:

• SameFunction: the calls must be made from inside the same function definition
• SameRootFunction: the calls must be defined in some shared encapsulating function definition
• File (default): the calls can be made anywhere in the same file

rules: {
  "console-time-pairs/console-time-pairs": ["error", {
    "scope": "SameFunction" | "SameRootFunction" | "File",
  }],
},

Example

console.time("A"); // Will always produce a warning

function() {
  console.time("B"); //    Will produce a warning with "SameFunction", "SameRootFunction"
}
function() {
  console.timeEnd("B"); // Will produce a warning with "SameFunction", "SameRootFunction"
}
function() {
  setTimeout(() => console.time("C"), 100); //    Will only produce a warning with "SameFunction"
  setTimeout(() => console.timeEnd("C"), 200); // Will only produce a warning with "SameFunction"
}
function() {
  console.time("D"); //    Will never produce a warning
  console.timeEnd("D"); // Will never produce a warning
}

Limitations

If the label argument is not a string literal the plugin will attempt to match using the text of the source code. This handles many cases, such as: using a shared label variable, using identical string-template expressions, concatenating strings in the same way, etc.

However, it can still generate false positives if the expressions are not identical. In those cases using lint-skips, or extracting out a variable for the timer label should resolve the issue.