Angular 9 release | New Breaking Changes | How to update app to Angular 9

Angular now compiles with Ivy by default.
CLI apps compile in AOT mode by default (which includes template type-checking). Users who only built with JIT before may see new type errors.
Typescript 3.4 and 3.5 are no longer supported. Please update to Typescript 3.7.
tslib is now listed as a peer dependency rather than a direct dependency. If you are not using the CLI, you must manually install tslib, using yarn add tslib or npm install tslib --save.
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Angular release information
Angular update Guide
Angular AOT information
Angular Ivy information
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In Version 9, Angular Ivy is the default rendering engine.
Rendering engine takes component class and template and generate HTML and Javascript code because browser doesn't understand angular syntax
so Ivy is the code name for Angular's next-generation compilation and rendering pipeline. With the version 9 release of Angular, the new compiler and runtime instructions are used by default instead of the older compiler and runtime, known as View Engine.

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