Determine if an object in Angular only consists of null values using *ngIf

Question

Determine if an object in Angular only consists of null values using *ngIf

To determine if the object itself is null, one can use (myObj | keyvalue)?.length. ()

In JavaScript, checking if an object contains only null values can be done with

Object.values(myObj).some(x => x !== null)

. However, attempting to utilize this in the template results in

Parser Error: Bindings cannot contain assignments

.

Is there a method to verify if myObj exclusively holds null values within the template, or should a separate function be employed?

javascript angular typescript angular-ng-if

Answer 1

Answer №1

To achieve this functionality, you need to develop a custom pipe called EveryPipe.

@Pipe({ name: 'every' })
export class ContainsPipe implements PipeTransform {
   transform(input: any, value: any): boolean {
      return Object.values(input).every(x => x == value)
   }
}

You can use it as shown below:

<div *ngIf="(myObj | every:null)"> 
   ...
</div>

Answer 2

To achieve this functionality, you need to develop a custom pipe called EveryPipe.

@Pipe({ name: 'every' })
export class ContainsPipe implements PipeTransform {
   transform(input: any, value: any): boolean {
      return Object.values(input).every(x => x == value)
   }
}

You can use it as shown below:

<div *ngIf="(myObj | every:null)"> 
   ...
</div>

Answer 3

Answer №2

The issue at hand is clear from the error message. The template parser is unable to assign values to variables directly. Attempting to assign the values of myObj to a local variable x is done in order to check for any values equal to null.

To achieve your desired outcome, you will need to either create a method within the component or utilize a pipe. One approach is to use a function like this:

.html:

<div *ngIf="containsOnlyNullValues(myObj)">
  // Your conditional content here...
</div>

.ts:

public containsOnlyNullValues(myObj: any) {
  return Object.values(myObj).some(x => x !== null);
}

Please note that in some cases, you can save the result of a condition as a variable for later use in the template. However, this is an exception rather than the norm.

Answer 4

The issue at hand is clear from the error message. The template parser is unable to assign values to variables directly. Attempting to assign the values of myObj to a local variable x is done in order to check for any values equal to null.

To achieve your desired outcome, you will need to either create a method within the component or utilize a pipe. One approach is to use a function like this:

.html:

<div *ngIf="containsOnlyNullValues(myObj)">
  // Your conditional content here...
</div>

.ts:

public containsOnlyNullValues(myObj: any) {
  return Object.values(myObj).some(x => x !== null);
}

Please note that in some cases, you can save the result of a condition as a variable for later use in the template. However, this is an exception rather than the norm.

Determine if an object in Angular only consists of null values using *ngIf

Answer №1

Answer №2

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