Angular 8 Input validation accept only numbers

Here's a simpler approach using a directive.

export class NumbersOnlyDirective {
    @Input('field') field;

    constructor(private ngControl: NgControl) { }

    @HostListener('input', ['$event']) onInput(event): void {
        if (this.field === 'price') {
            const value = event.target.value;
            this.ngControl.control.setValue(parseFloat(value) || 0);
            if (value.slice(-1) === '.' && !value.slice(0, -1).includes('.')) {
                event.target.value = value;
            }
        }
    }
}

This directive will only allow decimal numbers to be entered. parseFloat removes the alphabets and other special characters. I have used || 0 as a fallback in case the field is emptied but if you don't want anything to display, simply use || '' instead. The if condition ensures that only one decimal point can be entered unlike when you use type="number" (type="number" will also change the ngModel to a string). The condition is placed after we update the control value so that if the last entered value is a ., the ngModel value will not include the . while the view will contain it.

Then use this directive in your template like below and pass the field value so that the this logic will only apply to the price field.

<input [required]="required" numbersOnly [field]="hitem.field" [name]="item[hitem.field]" [(ngModel)]="item[hitem.field]" />

Here is a working example on StackBlitz.

To do it dynamically,

include type in columnDefs objects:

Working Demo

 columnDefs = [
    { headerName: "Make", field: "make", edit: true, type: "text" },
    { headerName: "Model", field: "model", dropdown: true, type: "text" },
    { headerName: "Price", field: "price", edit: true, type: "number" }
  ];

Template:

<input [required]="required" [type]="hitem.type" [name]="item[hitem.field]" [(ngModel)]="item[hitem.field]" />

You can achieve by using directive.

@Directive({
  selector: "input[numbersOnly]"
})
export class NumberDirective {
  constructor(private _el: ElementRef) {}
  @HostListener("keydown", ["$event"])
  onKeyDown(e: KeyboardEvent) {
    if (
      // Allow: Delete, Backspace, Tab, Escape, Enter
      [46, 8, 9, 27, 13].indexOf(e.keyCode) !== -1 ||
      (e.keyCode === 65 && e.ctrlKey === true) || // Allow: Ctrl+A
      (e.keyCode === 67 && e.ctrlKey === true) || // Allow: Ctrl+C
      (e.keyCode === 86 && e.ctrlKey === true) || // Allow: Ctrl+V
      (e.keyCode === 88 && e.ctrlKey === true) || // Allow: Ctrl+X
      (e.keyCode === 65 && e.metaKey === true) || // Cmd+A (Mac)
      (e.keyCode === 67 && e.metaKey === true) || // Cmd+C (Mac)
      (e.keyCode === 86 && e.metaKey === true) || // Cmd+V (Mac)
      (e.keyCode === 88 && e.metaKey === true) || // Cmd+X (Mac)
      (e.keyCode >= 35 && e.keyCode <= 39) // Home, End, Left, Right
    ) {
      return; // let it happen, don't do anything
    }
    // Ensure that it is a number and stop the keypress
    if (
      (e.shiftKey || (e.keyCode < 48 || e.keyCode > 57)) &&
      (e.keyCode < 96 || e.keyCode > 105)
    ) {
      e.preventDefault();
    }
  }
}

Show the directive in html,

 <input [required]="required" [name]="item[hitem.field]" [(ngModel)]="item[hitem.field]" numbersOnly/>

Declare the directive in AppModule

@NgModule({
  imports:      [ BrowserModule, FormsModule ],
  declarations: [ AppComponent, HelloComponent,NumberDirective ],
  bootstrap:    [ AppComponent ]
})

Working Stackblitz

Update 1

If you like to allow numbers only in price field only:

<input [required]="required" [name]="item[hitem.field]" [(ngModel)]="item[hitem.field]" [numbersOnly]="hitem.headerName!='Make'"/>

and in directive,

export class NumberDirective {
  @Input() numbersOnly:boolean;
  constructor(private _el: ElementRef) {}
  @HostListener("keydown", ["$event"])
  onKeyDown(e: KeyboardEvent) {
    if(!this.numbersOnly)
      return;
    ....// rest of codes
}

Add type="number" in your input element

<input [required]="required"  [name]="item[hitem.field]" [(ngModel)]="item[hitem.field]" type="number" />

If you want to change input type dynamically then [type]="type" & in your .ts file set type="text | number | email | tel, etc"

@Directive({
    selector: '[cdeCurrencyPipe]',
})
export class CDECurrencyPipe {
    private navigationKeys = ['Backspace','Delete','Tab','Escape','Enter','Home','End','ArrowLeft','ArrowRight','Clear','Copy','Paste'];
    @Input() OnlyNumber: boolean;
   
    constructor(private control : NgControl, 
            private elementRef: ElementRef,
            private currencyPipe: CurrencyPipe) { }

    @HostListener('blur', ['$event.target.value'])
    onBlur(raw) {
        if(raw && raw.length > 0){
            var strVal = raw.replace(/[$,]/g,"");
            this.elementRef.nativeElement.value = this.currencyPipe.transform(strVal);
        }
    }

    @HostListener('focus', ['$event.target.value'])
    onChange(raw) {
        if(raw && raw.length > 0){
            var strVal = raw.replace(/[$,]/g,"");
            this.control.valueAccessor.writeValue(strVal)
        }
    }

    @HostListener('keydown', ['$event'])
    onKeyDown(e: KeyboardEvent) {
        if (
            // Allow: Delete, Backspace, Tab, Escape, Enter, etc
            this.navigationKeys.indexOf(e.key) > -1 || // Allow: navigation keys: backspace, delete, arrows etc.
            (e.key === 'a' && e.ctrlKey === true) || // Allow: Ctrl+A
            (e.key === 'c' && e.ctrlKey === true) || // Allow: Ctrl+C
            (e.key === 'v' && e.ctrlKey === true) || // Allow: Ctrl+V
            (e.key === 'x' && e.ctrlKey === true) || // Allow: Ctrl+X
            (e.key === 'a' && e.metaKey === true) || // Allow: Cmd+A (Mac)
            (e.key === 'c' && e.metaKey === true) || // Allow: Cmd+C (Mac)
            (e.key === 'v' && e.metaKey === true) || // Allow: Cmd+V (Mac)
            (e.key === 'x' && e.metaKey === true) // Allow: Cmd+X (Mac)
            ) {
            // let it happen, don't do anything
            return;
        }
        // Ensure that it is a number and stop the keypress
        if (
            (e.shiftKey || (e.keyCode < 48 || e.keyCode > 57)) &&
            (e.keyCode < 96 || e.keyCode > 105)
        ) {
            e.preventDefault();
        }
    }
}

It can be done as follow:

in component.html

<input (keypress)="numberOnly($event)" type="text">

in component.ts

numberOnly(event): boolean {
  const charCode = (event.which) ? event.which : event.keyCode;
    if (charCode > 31 && (charCode < 48 || charCode > 57)) {
       return false;
    }
    return true;

}

Add validation like this

sufficient_observation_count: new FormControl( 0,[Validators.pattern("^(0|[1-9][0-9]{0,100})$"),Validators.required])

The pattern will check that first digit shoud be whether 0 or from 1 to 9,and then subsequent 100 digits can be from 0 to 9,so it checks for decimals,negative numbers,exponentials etc.

Instead of using keycode to detect the input (whether char or number) its better to use regular expression to match the input type. Below is a directive doing that. The advantage of using regex is that your code becomes flexible. For example if you need to limit number of digits in your decimal number to 7 max & decimal places to 2 then you can simply change the regex to /^[0-9]{1,7}(.[0-9]{0,2}){0,1}$/g

@Directive({
  selector: '[allowNumbers]'
})
export class AllowOnlyNumbersDirective {

    private decRegex: RegExp = new RegExp(/^[0-9]+(\.[0-9]*){0,1}$/g); 
      private specialKeys: Array<string> = ['Backspace', 'Tab', 'End', 'Home', 'ArrowLeft', 'ArrowRight', 'Delete', 'Enter', 'Control', 'Cut', 'Copy', 'Paste'];
    
      targetElement: any;
    
      constructor(element: ElementRef) {
        this.targetElement = element.nativeElement;
    
      }
    
      @HostListener('paste', ['$event'])
      onPaste(event: ClipboardEvent) {
    
        const pastedValue = event.clipboardData.getData('text/plain');
        console.log(pastedValue);
    
        if (pastedValue && !String(pastedValue).match(this.decRegex)) {
            event.preventDefault(); //prevent the paste from happening
        }
    
      }
    
    
      @HostListener('keydown', ['$event'])
      onKeyDown(event: KeyboardEvent) {
    
        if (this.specialKeys.indexOf(event.key) !== -1) {
          return; //if any of the special keys like backspace, delete, arrow keys etc. are pressed, then return
        }
    
        const inputTextBoxValue: string = this.targetElement.value.concat(event.key); //concatenate the previous value with the new typed value
    
        console.log(`event.key: ${event.key}, inputValue: ${inputTextBoxValue}`);
    
        if (inputTextBoxValue && !String(inputTextBoxValue).match(this.decRegex)) {
          event.preventDefault(); //if its not a number then prevent the keypress
        }
    
        return;
    
      }
    
    }

Usage:

<input allowOnlyNumbers type = "text" id = "someId" formControlName = "someName" />