How to check javascript code

When writing JavaScript code, sometimes we need to perform code inspections to ensure the quality and readability of the code. Code inspection can help us discover some possible errors and irregular writing, so that early detection of problems can allow us to fix problems faster, thereby reducing unnecessary development costs. In this article, I'll explain how to use two different tools to inspect JavaScript code.

1. Use the Lint tool

ESLint is a very popular code checking tool that can check your JavaScript code and help you find possible problems. ESLint has a very extensive set of rules that can help you find problems that traditional compilers cannot. At the same time, ESLint can also expand its functions by customizing rules to meet various needs.

1. Installing ESLint

Before we start using ESLint, we need to install ESLint locally. Before installation, we need to install Node.js and npm. These two tools must be installed on your computer before you can continue with the following steps.

To install ESLint, run the following command in the terminal:

npm install eslint --save-dev

After the installation is complete, you can use ESLint to check your JavaScript code.

2. Configuring ESLint

Before using ESLint, we need to configure rules for it so that it can correctly check our code. ESLint can load configuration through the .eslintrc.json file.

We can create a .eslintrc.json file in the root directory of the project and define the rules we need in it. The following is a sample ESLint configuration file:

{
  "parserOptions": {
    "ecmaVersion": 8,
    "sourceType": "module"
  },
  "extends": ["eslint:recommended"],
  "rules": {
    "no-console": "warn",
    "no-unused-vars": "warn"
  }
}

In this sample configuration, we specify that ESLint uses the ECMAScript 8 version and uses module import. We also specified some rules, such as requiring warnings about unused variables and warnings about console.log statements.

3. Run ESLint

After completing the configuration, we can use the following command to run ESLint:

./node_modules/.bin/eslint your-file.js

This command will run on your JavaScript code Check, and output errors and warnings. You can display different results, such as only errors or warnings, by running ESLint with different command line options.

2. Use Prettier

Prettier is a tool that automatically formats code. It can help us unify the style and format of the code and improve the readability and maintainability of the code. When we write code, Prettier can automatically adjust the code's indentation, spaces, semicolons and other formats, and ensure that the code style and specifications are consistent.

1. Install Prettier

To install Prettier, run the following command in the terminal:

npm install prettier --save-dev

After the installation is complete, you can use Prettier to your The code has been formatted.

2. Configuring Prettier

Similar to ESLint, Prettier can also load rules through a configuration file. Prettier can support almost all code editors, such as Visual Studio Code, Atom, etc.

In Visual Studio Code, we can add the following configuration in the workspace settings:

{
  "editor.defaultFormatter": "esbenp.prettier-vscode",
  "[javascript]": {
    "editor.formatOnSave": true
  }
}

This configuration will enable the Prettier plugin and automatically format code when saving JavaScript files.

3. Run Prettier

After completing the configuration, we can use the following command to run Prettier:

npx prettier your-file.js

This command will run on your JavaScript code Format and output the formatted code. You can use different command line options to adjust the behavior of code formatting.

Summary

Through the above introduction, we can find that JavaScript code inspection and formatting are very important and can help us improve code quality, readability and maintainability. ESLint and Prettier are two very practical tools that you can install and configure according to the above steps to improve your coding efficiency and code quality.

The above is the detailed content of How to check javascript code. For more information, please follow other related articles on the PHP Chinese website!