Directive to upper case input fields

问题

I want to use a directive to transform all input data to uppercase. To achieve that, I create this custom directive :

@Directive({
  selector: '[appToUpperCase]'
})
export class ToUpperCaseDirective {

  constructor() {}

  @HostListener('input', ['$event']) onKeyUp(event) {
    event.target['value'] = event.target['value'].toUpperCase();
  }

}

And I use it like that :

<form [formGroup]="formGroup" appToUpperCase>

It works almost good exept that when I enter text in my field, the upper case transform is permormed but the focus is set at the end of the field...So when I edit a pre filled input, if I want to modify the begining of the data, I have to set the focus at the right place after each Keyup event...

How can I fix that ?

回答1:

I developed a solution in Angular 7 for uppercase and lowercase, based in some posts i've read. But i tested only for reactive forms. This solution resolve the problem of the last word and the position of the cursor.

// user.component.html
<input  type="text" name="name" class="form-control" formControlName="name" uppercase />


// user.component.ts
import { Directive, ElementRef, HostListener } from '@angular/core';
@Directive({
selector: '[uppercase]',
  host: {
    '(input)': '$event'
  }
})
export class UppercaseInputDirective {

  lastValue: string;

  constructor(public ref: ElementRef) { }

  @HostListener('input', ['$event']) onInput($event) 
  {
    var start = $event.target.selectionStart;
    var end = $event.target.selectionEnd;
    $event.target.value = $event.target.value.toUpperCase();
    $event.target.setSelectionRange(start, end);
    $event.preventDefault();

    if (!this.lastValue || (this.lastValue && $event.target.value.length > 0 && this.lastValue !== $event.target.value)) {
      this.lastValue = this.ref.nativeElement.value = $event.target.value;
      // Propagation
      const evt = document.createEvent('HTMLEvents');
      evt.initEvent('input', false, true);
      event.target.dispatchEvent(evt);
    }
  }
}

I posted here in stackblitz

回答2:

Basically when you modify the value from imperative code, it becomes difficult manage position of cursor. When you re-write value input value, it throws cursor at the start of input.

I'd recommend you to go for CSS way. More cleaner

[my-attribute] input { text-transform: uppercase; }

回答3:

Pankaj's idea it's better than create a directive. You only must send data.toUpperCase(). Anyway if you want use a directive like this. Be careful, not only we must use preventDefault(), we must dispatch event change

import { Directive,HostListener } from '@angular/core';

@Directive({
  selector: '[appToUpperCase]'
})
export class ToUpperCaseDirective {

  constructor() { }

  @HostListener('keydown', ['$event']) onKeyDown(event:KeyboardEvent) {
    if (event.keyCode>32 && event.keyCode<128)
   {
      event.target['value']+=event.key.toUpperCase();
      event.preventDefault(); //stop propagation
      //must create a "input" event, if not, there are no change in your value
      var evt = document.createEvent("HTMLEvents");
      evt.initEvent("input", false, true);
      event.target.dispatchEvent(evt);
    }

  }

}

回答4:

import { Directive, ElementRef, HostListener } from '@angular/core';

@Directive({
  selector: '[lowercaser]'
})
export class LowerCaserDirective {

  lastValue: string;

  constructor(public ref: ElementRef) {
  }

  @HostListener('input', ['$event']) onInput(event) {
    const resEventValue = event.target.value.toLowerCase();
    // Avoid max call
    if (!this.lastValue || (this.lastValue && event.target.value.length > 0 && this.lastValue !== resEventValue)) {
      this.lastValue = this.ref.nativeElement.value = resEventValue;
      // Propagation
      const evt = document.createEvent('HTMLEvents');
      evt.initEvent('input', false, true);
      event.target.dispatchEvent(evt);
    }
  }

}

来源：https://stackoverflow.com/questions/46825078/directive-to-upper-case-input-fields

标签

angular

directive

uppercase