Import/require this script into your nativescript app.ts to add a 'deleteTap' event to all your TextField components. This will fire a 'deleteTap' event when the user presses backspace, even when the text field is empty.

nativescript-textfield-deletetap-patch.js

import { isAndroid, isIOS } from '@nativescript/core/platform'
import { layout } from '@nativescript/core/utils'
import { TextField } from '@nativescript/core/ui/text-field'

if(isIOS){
	let UITextFieldImpl = (function (_super) {
		__extends(UITextFieldImpl, _super)

		function UITextFieldImpl() {
			return _super !== null && _super.apply(this, arguments) || this
		}

		UITextFieldImpl.initWithOwner = function (owner) {
			let handler = UITextFieldImpl.new()

			handler._owner = owner

			return handler
		}

		UITextFieldImpl.prototype._getTextRectForBounds = function (bounds) {
			let owner = this._owner ? this._owner.get() : null

			if (!owner) {
				return bounds
			}

			let size = bounds.size
			let x = layout.toDeviceIndependentPixels(owner.effectiveBorderLeftWidth + owner.effectivePaddingLeft)
			let y = layout.toDeviceIndependentPixels(owner.effectiveBorderTopWidth + owner.effectivePaddingTop)
			let width = layout.toDeviceIndependentPixels(layout.toDevicePixels(size.width) - (owner.effectiveBorderLeftWidth + owner.effectivePaddingLeft + owner.effectivePaddingRight + owner.effectiveBorderRightWidth))
			let height = layout.toDeviceIndependentPixels(layout.toDevicePixels(size.height) - (owner.effectiveBorderTopWidth + owner.effectivePaddingTop + owner.effectivePaddingBottom + owner.effectiveBorderBottomWidth))
			
			return CGRectMake(x, y, width, height)
		}

		UITextFieldImpl.prototype.textRectForBounds = function (bounds) {
			return this._getTextRectForBounds(bounds)
		}

		UITextFieldImpl.prototype.editingRectForBounds = function (bounds) {
			return this._getTextRectForBounds(bounds)
		}

		UITextFieldImpl.prototype.deleteBackward = function () {
			let owner = this._owner ? this._owner.get() : null

			if (owner) {
				owner.notify({eventName: 'deleteTap', object: owner})
			}

			return _super.prototype.deleteBackward.call(this)
		}

		return UITextFieldImpl
	}(UITextField))

	TextField.prototype.createNativeView = function() {
		return UITextFieldImpl.initWithOwner(new WeakRef(this))
	}

}else if(isAndroid){
	let orgCreateNativeView = TextField.prototype.createNativeView

	TextField.prototype.createNativeView = function() {
		let nativeView = orgCreateNativeView.apply(this, arguments)

		nativeView.setOnKeyListener(new android.view.View.OnKeyListener({
			onKey: (view, keyCode, keyevent) => {
				if(keyCode == android.view.KeyEvent.KEYCODE_DEL){
					this.notify({eventName: 'deleteTap', object: this})
				}

				return false
			}
		}))

		return nativeView
	}
}