How to retrieve the value of an input field in Angular 2/Typescript without using ngModel

Question

How to retrieve the value of an input field in Angular 2/Typescript without using ngModel

Currently, I'm utilizing Typescript in conjunction with Angular2, mirroring the structure of the Angular2 Tour of Heroes guide.

There is a specific input field that I aim to associate a change event with, triggering custom logic whenever the value within the field is altered. In order to facilitate this, it's crucial for me to access the current value of the field before any changes take place. Consequently, employing ngModel to bind the field would not be ideal as it could potentially overwrite the property prior to retrieving its original value.

This results in something similar to the following setup:

<input (change)="handleChange(myObj, $event)" value={{ myObj.myField }}... />

Subsequently, within the handleChange function:

handleChange(obj: MyObjectClass, e: Event) {
  let oldValue: number = obj.myField;
  let newValue : number = parseInt(e.target.value);

  // Implement necessary logic

  obj.myField = newValue;
}

Despite functioning correctly in terms of functionality, an error has been presented by the Typescript compiler which reads

error TS2339: Property 'value' does not exist on type 'EventTarget'.

, specifically referring to the line

newValue : number = parseInt(e.target.value);

Are there more efficient methods to achieve the same result?

javascript angular typescript

Answer 1

Answer №1

Instead of relying on the change event for input validation, it is advisable to create a custom validator. However, if you still want to access the input value, you can do so by using a reference to the input element as shown below:

<input #myInput (change)="handleChange(myInput.value, $event)" value={{ myObj.myField }}... />

Answer 2

Instead of relying on the change event for input validation, it is advisable to create a custom validator. However, if you still want to access the input value, you can do so by using a reference to the input element as shown below:

<input #myInput (change)="handleChange(myInput.value, $event)" value={{ myObj.myField }}... />

Answer 3

Answer №2

When examining the definition of EventTarget, it appears as follows:

 interface EventTarget {
   addEventListener(type: string, listener: EventListenerOrEventListenerObject, useCapture?: boolean): void;
   dispatchEvent(evt: Event): boolean;
   removeEventListener(type: string, listener: EventListenerOrEventListenerObject, useCapture?: boolean): void;
 }

The value property is not included in this definition. Therefore, to access it correctly, you can use:

 e.target['value']

The reason for excluding the value property from EventTarget is to accommodate different types of events. For example, when using the same Event for an input type checked, you may want to access the checked property instead.

Answer 4

When examining the definition of EventTarget, it appears as follows:

 interface EventTarget {
   addEventListener(type: string, listener: EventListenerOrEventListenerObject, useCapture?: boolean): void;
   dispatchEvent(evt: Event): boolean;
   removeEventListener(type: string, listener: EventListenerOrEventListenerObject, useCapture?: boolean): void;
 }

The value property is not included in this definition. Therefore, to access it correctly, you can use:

 e.target['value']

The reason for excluding the value property from EventTarget is to accommodate different types of events. For example, when using the same Event for an input type checked, you may want to access the checked property instead.

Answer 5

Answer №3

The events in Angular2 do not provide direct access to the event's target. It is recommended to avoid accessing values directly from the element and instead use bindings.

whatever.component.ts

export class WhateverComponent {
    private tempValue: any;

    private handleEventChange(obj: MyObjectClass, e: Event) {
        obj.field = this.tempField;
    }
}

whatever.component.html

<input (change)="handleEventChange(myObj, $event)" [value]="tempValue" />

If there is a need to access the element directly, you can utilize the ElementRef class. However, be aware that this approach poses security risks as mentioned in the documentation:

Allowing direct access to the DOM can increase vulnerability to XSS attacks. Exercise caution when using ElementRef in your code. Refer to the Security Guide for more information.

Answer 6

The events in Angular2 do not provide direct access to the event's target. It is recommended to avoid accessing values directly from the element and instead use bindings.

whatever.component.ts

export class WhateverComponent {
    private tempValue: any;

    private handleEventChange(obj: MyObjectClass, e: Event) {
        obj.field = this.tempField;
    }
}

whatever.component.html

<input (change)="handleEventChange(myObj, $event)" [value]="tempValue" />

If there is a need to access the element directly, you can utilize the ElementRef class. However, be aware that this approach poses security risks as mentioned in the documentation:

Allowing direct access to the DOM can increase vulnerability to XSS attacks. Exercise caution when using ElementRef in your code. Refer to the Security Guide for more information.

Answer 7

Answer №4

The most straightforward approach is to utilize the official Extracting user input from a template reference variable. This method ensures that the interaction occurs solely within the confines of your Template, leaving the Component untouched. For instance:

<input (change)="handleChange(myObj, newValue.value)" #newValue />

// The Method remains unchanged
handleChange (obj: MyObjectClass, e: Event) {
  oldValue: number = obj.myField;
  newValue : number = parseInt(e.target.value);

  // Implement some logic

  obj.myField = newValue;
}

An added perk is if you want to link the Enter key to the input field, you don't have to include the cumbersome if($event.keyCode == 13) ... condition; instead, leverage the Key event filtering feature by simply using:

(keyup.enter)="onEnter(newvalue.value)"

Answer 8

The most straightforward approach is to utilize the official Extracting user input from a template reference variable. This method ensures that the interaction occurs solely within the confines of your Template, leaving the Component untouched. For instance:

<input (change)="handleChange(myObj, newValue.value)" #newValue />

// The Method remains unchanged
handleChange (obj: MyObjectClass, e: Event) {
  oldValue: number = obj.myField;
  newValue : number = parseInt(e.target.value);

  // Implement some logic

  obj.myField = newValue;
}

An added perk is if you want to link the Enter key to the input field, you don't have to include the cumbersome if($event.keyCode == 13) ... condition; instead, leverage the Key event filtering feature by simply using:

(keyup.enter)="onEnter(newvalue.value)"

How to retrieve the value of an input field in Angular 2/Typescript without using ngModel

Answer №1

Answer №2

Answer №3

Answer №4

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