What is the equivalent of ngShow and ngHide in Angular 2+?

问题

I have a number of elements that I want to be visible under certain conditions.

In AngularJS I would write

<div ng-show=\"myVar\">stuff</div>

How can I do this in Angular 2+?

回答1:

Just bind to the hidden property

[hidden]="!myVar"

See also

• https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/hidden

issues

hidden has some issues though because it can conflict with CSS for the display property.

See how some in Plunker example doesn't get hidden because it has a style

:host {display: block;}

set. (This might behave differently in other browsers - I tested with Chrome 50)

workaround

You can fix it by adding

[hidden] { display: none !important;}

To a global style in index.html.

another pitfall

hidden="false"
hidden="{{false}}"
hidden="{{isHidden}}" // isHidden = false;

are the same as

hidden="true"

and will not show the element.

hidden="false" will assign the string "false" which is considered truthy.
Only the value false or removing the attribute will actually make the element visible.

Using {{}} also converts the expression to a string and won't work as expected.

Only binding with [] will work as expected because this false is assigned as false instead of "false".

*ngIf vs [hidden]

*ngIf effectively removes its content from the DOM while [hidden] modifies the display property and only instructs the browser to not show the content but the DOM still contains it.

回答2:

Use the [hidden] attribute:

[hidden]="!myVar"

Or you can use *ngIf

*ngIf="myVar"

These are two ways to show/hide an element. The only difference is: *ngIf will remove the element from DOM while [hidden] will tell the browser to show/hide an element using CSS display property by keeping the element in DOM.

回答3:

I find myself in the same situation with the difference than in my case the element was a flex container.If is not your case an easy work around could be

[style.display]="!isLoading ? 'block' : 'none'"

in my case due to the fact that a lot of browsers that we support still need the vendor prefix to avoid problems i went for another easy solution

[class.is-loading]="isLoading"

where then the CSS is simple as

&.is-loading { display: none } 

to leave then the displayed state handled by the default class.

回答4:

Sorry, I have to disagree with binding to hidden which is considered to be unsafe when using Angular 2. This is because the hidden style could be overwritten easily for example using

display: flex;

The recommended approach is to use *ngIf which is safer. For more details, please refer to the official Angular blog. 5 Rookie Mistakes to Avoid with Angular 2

<div *ngIf="showGreeting">
   Hello, there!
</div>

回答5:

If your case is that the style is display none you can also use the ngStyle directive and modify the display directly, I did that for a bootstrap DropDown the UL on it is set to display none.

So I created a click event for "manually" toggling the UL to display

<div class="dropdown">
    <button class="btn btn-default" (click)="manualtoggle()"  id="dropdownMenu1" >
    Seleccione una Ubicación
    <span class="caret"></span>
    </button>
    <ul class="dropdown-menu" [ngStyle]="{display:displayddl}">
        <li *ngFor="let object of Array" (click)="selectLocation(location)">{{object.Value}}</li>                                
     </ul>
 </div>    

Then on the component I have showDropDown:bool attribute that I toggle every time, and based on int, set the displayDDL for the style as follows

showDropDown:boolean;
displayddl:string;
manualtoggle(){
    this.showDropDown = !this.showDropDown;
    this.displayddl = this.showDropDown ? "inline" : "none";
}

回答6:

According to Angular 1 documentation of ngShow and ngHide, both of these directive adds the css style display: none !important;, to the element according to the condition of that directive (for ngShow adds the css on false value, and for ngHide adds the css for true value).

We can achieve this behavior using Angular 2 directive ngClass:

/* style.css */
.hide 
{
    display: none !important;
}

<!-- old angular1 ngShow -->
<div ng-show="ngShowVal"> I'm Angular1 ngShow... </div>

<!-- become new angular2 ngClass -->
<div [ngClass]="{ 'hide': !ngShowVal }"> I'm Angular2 ngShow... </div>

<!-- old angular2 ngHide -->
<div ng-hide="ngHideVal"> I'm Angular1 ngHide... </div>

<!-- become new angular2 ngClass -->
<div [ngClass]="{ 'hide': ngHideVal }"> I'm Angular2 ngHide... </div>

Notice that for show behavior in Angular2 we need to add ! (not) before the ngShowVal, and for hide behavior in Angular2 we don't need to add ! (not) before the ngHideVal.

回答7:

<div [hidden]="myExpression">

myExpression may be set to true or false

回答8:

If you are using Bootstrap is as simple as this:

<div [class.hidden]="myBooleanValue"></div>

回答9:

in bootstrap 4.0 the class "d-none" = "display: none!important;"

<div [ngClass]="{'d-none': exp}"> </div>

回答10:

For anybody else stumbling across this issue, this is how I accomplished it.

import {Directive, ElementRef, Input, OnChanges, Renderer2} from "@angular/core";

@Directive({
  selector: '[hide]'
})
export class HideDirective implements OnChanges {
  @Input() hide: boolean;

  constructor(private renderer: Renderer2, private elRef: ElementRef) {}

  ngOnChanges() {
    if (this.hide) {
      this.renderer.setStyle(this.elRef.nativeElement, 'visibility', 'hidden');
    } else {
      this.renderer.setStyle(this.elRef.nativeElement, 'visibility', 'visible');
    }
  }
}

I used 'visibility' because I wanted to preserve the space occupied by the element. If you did not wish to do so, you could just use 'display' and set it to 'none';

You can bind it to your html element, dynamically or not.

<span hide="true"></span>

or

<span [hide]="anyBooleanExpression"></span>

回答11:

Use hidden like you bind any model with control and specify css for it:

HTML:

<input type="button" class="view form-control" value="View" [hidden]="true" />

CSS:

[hidden] {
   display: none;
}

回答12:

<div [hidden]="flagValue">
---content---
</div>

回答13:

for me, [hidden]=!var has never worked.

So, <div *ngIf="expression" style="display:none;">

And, <div *ngIf="expression"> Always give correct results.

回答14:

There are two examples on Angular documents https://angular.io/guide/structural-directives#why-remove-rather-than-hide

A directive could hide the unwanted paragraph instead by setting its display style to none.

<p [style.display]="'block'">
  Expression sets display to "block".
  This paragraph is visible.
</p>

<p [style.display]="'none'">
  Expression sets display to "none".
  This paragraph is hidden but still in the DOM.
</p>

You can use [style.display]="'block'" to replace ngShow and [style.display]="'none'" to replace ngHide.

回答15:

Best way to deal with this issue using ngIf Because this well prevent getting that element render in front-end,

If you use [hidden]="true" or style hide [style.display] it will only hide element in front end and someone can change the value and visible it easily, In my opinion best way to hide element is ngIf

<div *ngIf="myVar">stuff</div>

and also If you have multiple element (need to implement else also) you can Use <ng-template> option

<ng-container *ngIf="myVar; then loadAdmin else loadMenu"></ng-container>
<ng-template #loadMenu>
     <div>loadMenu</div>
</ng-template>

<ng-template #loadAdmin>
     <div>loadAdmin</div>
</ng-template>  

sample ng-template code

回答16:

To hide and show div on button click in angular 6.

Html Code

<button (click)=" isShow=!isShow">FormatCell</button>
<div class="ruleOptionsPanel" *ngIf=" isShow">
<table>
<tr>
<td>Name</td>
<td>Ram</td>
</tr>
</table>
</div>

Component .ts Code

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent{
 isShow=false;
  }

this works for me and it is way to replace ng-hide and ng-show in angular6.

enjoy...

Thanks

来源：https://stackoverflow.com/questions/35578083/what-is-the-equivalent-of-ngshow-and-nghide-in-angular-2