Angular项目添加postinstall脚本“ngcc...”的原因及参数作用解析

云原生阿岚

2026-5-8

Understanding ngcc Parameters in Angular 9 Postinstall Scripts

Great question! Let's break down each of these ngcc flags to make sense of what they do, especially since the Ivy transition in Angular 9 had some specific tooling requirements:

--properties es2015 es5 browser module main
This flag tells ngcc which entry points (defined in a package's package.json) to process for Ivy compatibility. Each of these values corresponds to a standard field in npm packages:
- es2015/es5: Targets the ECMAScript version-specific builds of the package
- browser: Targets the browser-optimized build of the package
- module: Targets the ES module (ESM) entry point
- main: Targets the CommonJS (CJS) entry point
  By listing these properties, ngcc will generate Ivy-compatible versions for all these different build variants, ensuring your app can use the package regardless of which entry point Angular resolves.
--first-only
This flag limits ngcc to only process your project's direct dependencies (the ones listed directly in your package.json's dependencies section), rather than recursively processing every dependency of those dependencies. This speeds up the postinstall process significantly, as many transitive dependencies are either already Ivy-compatible or don't need reprocessing on every install.
--create-ivy-entry-points
This is the deprecated flag you mentioned. Instead of modifying the existing entry point files to make them Ivy-compatible, this flag would add new custom entry points (like __ivy_ngcc__ fields) to the package's package.json. The problem here is that Node.js and other module resolvers don't recognize these custom fields, which can lead to broken module resolution—hence why Angular's official docs recommend avoiding it. Modern ngcc instead patches the existing entry files in-place to add Ivy compatibility without altering the package.json structure.