? and ! symbol in Angular

 In Angular, both ! and ? serve different purposes and have specific meanings.

  1. !: This symbol is primarily used in Angular template expressions to indicate a non-null assertion. When you use ! after a property or expression, you're telling TypeScript that you're confident that the value won't be null or undefined. It's often used when you know for sure that a value exists, but TypeScript's static analysis cannot infer it.


    <div>{{ someVariable! }}</div>

    In this example, someVariable is assumed to exist and will not be null or undefined.

  2. ?: This symbol is known as the safe navigation operator or optional chaining operator. It's used to guard against null or undefined values when accessing properties of objects in Angular template expressions. If the property or expression before ? is null or undefined, the expression will return null instead of causing an error.


    <div>{{ object?.property }}</div>

    In this example, if object is null or undefined, Angular will not throw an error when trying to access property.

To summarize:

  • ! asserts that a value won't be null or undefined.
  • ? guards against null or undefined values when accessing properties.

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