ngshow

ngshow, also known as ng-show, is a directive in AngularJS (version 1.x) that conditionally displays an HTML element based on the truthiness of an Angular expression. When the expression evaluates to true, the element is shown; when it evaluates to false, the element is hidden. ngshow does not remove the element from the DOM; it toggles the element’s visibility.

How it works: ngshow watches the specified expression and updates the element as the value changes. Visibility is typically controlled by applying or removing a CSS class (commonly ng-hide) that hides the element, often via display: none !important in the default CSS. Because the element remains in the DOM, any child scopes or state inside the element are preserved when it is hidden and restored when shown.

Usage example: <div ng-show="isVisible">Content to display conditionally</div> Here, isVisible is a scope expression. If isVisible is true, the div is visible; if false, the div is hidden.

Relationship to other directives: ngshow is related to ng-hide, which hides the element when the expression is true, effectively the opposite behavior. ng-if is a different construct that removes and recreates the element in the DOM based on the condition, rather than merely toggling visibility.

Considerations: ngshow is useful for simple visibility toggling without altering the DOM structure, but it relies on CSS for hiding. For more complex conditional rendering that should not preserve the element, ng-if may be preferable. Performance can be affected if used extensively on large DOM trees with frequent expression changes.