Should I use ng-container when *ngIf="condition"?

When you use ngIf within a <p> tag versus using it with an <ng-container>, the primary difference lies in how the conditional rendering affects the DOM structure and styling. Here's a breakdown:

1. <p> ngIf="condition">

• DOM Structure:
  • If the condition is true, the <p> element and its content are added to the DOM.
  • If the condition is false, the <p> element and its content are removed from the DOM.
  • The <p> element itself is subject to the conditional rendering.
• Styling:
  • Any styling applied directly to the <p> element will be conditionally applied based on the ngIf condition.
  • The styling of the surrounding elements might be affected by the presence or absence of the <p> element.
• Use Cases:
  • Use this when you want to conditionally display a paragraph of text, and the paragraph itself is a meaningful semantic unit.
  • Suitable when the styling of the paragraph is relevant to the conditional logic.

Example:

<p *ngIf="isLoggedIn">Welcome, user!</p>

2. <ng-container *ngIf="condition">

• DOM Structure:
  • The <ng-container> element itself is not rendered in the DOM. It acts as a logical grouping element.
  • If the condition is true, the content within the <ng-container> is rendered.
  • If the condition is false, the content within the <ng-container> is removed from the DOM.
• Styling:
  • The <ng-container> does not introduce any styling of its own. It's a purely structural element.
  • The styling of the content within the <ng-container> is unaffected by the <ng-container> itself.
  • The surrounding elements styling will only be affected by the elements that are inside the ng-container.
• Use Cases:
  • Use this when you want to conditionally render a group of elements without adding an extra element to the DOM.
  • Ideal for applying conditional logic to a block of elements without affecting the layout or styling.
  • Useful when you want to use directives like *ngIf, or *ngFor, without adding extra html elements to the page.

Example:

<ng-container *ngIf="showDetails">
  <p>Name: John Doe</p>
  <p>Age: 30</p>
</ng-container>

Key Differences Summarized:

• DOM Element: <p> is a rendered element; <ng-container> is a logical grouping element that is not rendered.
• Styling effect: <p> affects styling, <ng-container> does not.
• Purpose: <p> is for conditional display of a paragraph; <ng-container> is for conditional display of a group of elements without adding extra DOM nodes.

In essence, <ng-container> is used for logical grouping and conditional rendering without affecting the DOM structure or styling, while <p> is used when you want to conditionally render a paragraph element itself.