Custom ESLint rules can unify code style and reduce bugs. First, understand the rules structure of ESLint based on AST and write detection logic, such as prohibiting the use of console.log; second, create a rule file in the project and configure .eslintrc.js to refer to the rules; finally, pay attention to the familiarity of AST structure, avoid false positives and missed reports, optimize performance and improve configurability. Through these three steps, custom rules can be implemented and integrated to improve team development efficiency and code quality.
It is important to maintain a consistent code style and quality when writing JavaScript code. Although ESLint provides a lot of built-in rules, sometimes you still need to customize some specific inspection logic according to project needs. Implementing custom ESLint rules is not complicated. As long as you understand the basic structure and process, you can easily get started.
Why use custom ESLint rules?
Many teams will have some conventional coding specifications during development, such as prohibiting the use of certain APIs, requiring functions to have JSDoc annotations, or restricting the use of specific variable names. These rules are difficult to override through common configurations, and you need to customize ESLint rules to enforce these specifications. It not only helps the team unify the code style, but also detects potential problems in advance and reduces the probability of bugs.
How to create a basic custom ESLint rule?
To write a custom rule, you must first understand the rule structure of ESLint. The ESLint rule is analyzed based on AST (Abstract Syntax Tree). You need to write a function to receive the current node and determine whether it meets expectations.
The simplest rule structure is as follows:
module.exports = {
create(context) {
return {
CallExpression(node) {
if (node.callee.name === 'console' && node.callee.property?.name === 'log') {
context.report({ node, message: 'Don't use console.log' });
}
},
};
},
}; In this example, we detect all places where console.log is called and prompt the developer to avoid using it. You can save this file as a .js file and then reference it in the ESLint configuration.
How to integrate custom rules into a project?
Integrating custom rules is mainly divided into three steps:
- Put the rule file in the right place, such as
eslint-rules/ - Add
rulesfield to your rules in the ESLint configuration file - Make sure ESLint loads these rules correctly
For example, in .eslintrc.js , you can configure it like this:
module.exports = {
// ...Other configuration rules: {
'no-console-log': ['error', require('./eslint-rules/no-console-log')],
},
};If you share these rules internally in the team, you can package them into npm packages to facilitate multiple projects reuse.
Frequently Asked Questions and Notes
When writing custom rules, there are several error-prone areas that need to be paid attention to:
- Unfamiliar with AST structure : It is recommended to use AST Explorer to view the node structure corresponding to different statements.
- False or underreport : In some cases, the rules may be triggered incorrectly or not, requiring careful testing of various boundary situations.
- Performance issues : If the rule processing logic is too heavy, it may affect the running speed of ESLint, especially in large projects, pay more attention to optimization.
- Rule configurability : If you want the rules to be flexibly adjusted according to different projects, you can add a
meta.schemafield tocreatemethod to support configuration items.
Basically that's it. Writing custom ESLint rules may be a bit of a barrier at the beginning, but once you master the basic routines, you will find that it is very practical and can greatly improve the code quality and consistency of the project.
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