如何限制输入文本框只能以 Angular2 形式输入数字？

Question

我必须限制用户只能在 Angular2->form 的字段中输入数字我有解决方案，但退格键在输入字段中不起作用任何人都可以对此有适当的解决方案吗？

form.html

<input (keypress)="keyPress($event)" minlength="8" maxlength="15" required />

form.component.ts

keyPress(event: any) {
    const pattern = /[0-9\+\-\ ]/;
    let inputChar = String.fromCharCode(event.charCode);
    // console.log(inputChar, e.charCode);
       if (!pattern.test(inputChar)) {
       // invalid character, prevent input
           event.preventDefault();
      }
 }

在 kepress 事件中，它限制用户只能输入数字，但此代码的问题是退格键，Tab 键不是 working.So，此代码与我的预期不符...

Answer 1

退格键不起作用，因为：event.charCode 不会映射到退格键的 0-9 数字之一。

您需要将退格键列入白名单（即 keyCode = 8）。像这样的东西（从我的头顶）：

if(event.keyCode != 8 && !pattern.test(inputChar)) {
   event.preventDefault();
}

Answer 2

我的回答是：- form.html:

form.component.ts

restrictNumeric = function (e) {
     var input;
     if (e.metaKey || e.ctrlKey) {
        return true;
     }
     if (e.which === 32) {
        return false;
     }
     if (e.which === 0) {
        return true;
     }
     if (e.which < 33) {
        return true;
     }
     input = String.fromCharCode(e.which);
     return !!/[\d\s]/.test(input);
 }

Answer 3

您可以通过以下方式使用正则表达式实现：

var numbersOnly = document.getElementById("numbersOnly");
numbersOnly.onkeyup = function myFunction() {
    numbersOnly.value = numbersOnly.value.replace(/[^0-9]/g, '');
};

<input id="numbersOnly" minlength="8" maxlength="15" required>

Answer 4

使用 html5 标签怎么样？ <input type="number">
所有浏览器都支持它。

https://www.w3schools.com/html/html_form_input_types.asp

Answer 5

你也可以这样用

keyPress(event: any) {

        const pattern = /[0-9\+\-\ ]/;
        let inputChar = String.fromCharCode(event.charCode);

            if (!pattern.test(inputChar) && event.charCode != '0') {
                event.preventDefault();
            }
    }

Answer 6

请不要再使用 String.fromCharCode(event.keyCode)，它已被标记为已弃用 MDN，而且它似乎无法在 Firefox 58 中正常工作。一个简单的功能，已在Chrome & 火狐：

onKeypress(event: any) {
  const keyChar = event.key;

  let allowCharacter: boolean;
  if (keyChar === "-" && event.target.selectionStart !== 0) {
    allowCharacter = false;
  }
  else if (
    keyChar === "Tab" ||
    keyChar === "Enter" ||
    keyChar === "Backspace" ||
    keyChar === "ArrowLeft" ||
    keyChar === "ArrowRight" ||
    keyChar === "Delete") {
    allowCharacter = true;
  }
  else {
    allowCharacter = (keyChar >= '0' && keyChar <= '9');
  }

  if (!allowCharacter) {
    event.preventDefault();
  }
}

我对这段代码也不满意，希望 Angular 中有更好的库。

Answer 7

我创建了一个只允许您键入数字的指令。

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


@Directive({
   selector: 'input[app-numeric-field]'
})
export class NumericValidatorDirective implements OnInit {
  @Input('app-numeric-field') maxLength: string;

  constructor(private elementRef: ElementRef,private _renderer: Renderer) {}

  ngOnInit(): void {
     this._renderer.setElementAttribute(this.elementRef.nativeElement, 'maxlength', this.maxLength);
  }

  @HostListener('keydown', ['$event']) onKeyDown(event) {
     let e = <KeyboardEvent> event;
        if ([46, 8, 9, 27, 13, 110].indexOf(e.keyCode) !== -1 ||
           // Allow: Ctrl+A
           (e.keyCode === 65 && (e.ctrlKey || e.metaKey)) ||
           // Allow: Ctrl+C
           (e.keyCode === 67 && (e.ctrlKey || e.metaKey)) ||
           // Allow: Ctrl+V
           (e.keyCode === 86 && (e.ctrlKey || e.metaKey)) ||
           // Allow: Ctrl+X
           (e.keyCode === 88 && (e.ctrlKey || e.metaKey)) ||
           // Allow: home, end, left, right
           (e.keyCode >= 35 && e.keyCode <= 39)) {
           // 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();
       }
    }
}

那你就可以这样用了

<input matInput app-numeric-field>

Answer 8

我制定了一个指令来阻止特定输入，类似于此处和其他帖子中发布的其他指令。我基于 this article，但做了一些更改以避免使用已弃用的 keyCode 属性等。

我还取消了对允许的键盘命令的限制（包含 Ctrl、Command、Shift 或 Alt 的任何组合键），因为它可能会导致意外限制（例如无法执行 undo/redo 命令）。

指令如下：

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

@Directive({
  selector: '[inputDigitsOnly]',
})
export class InputDigitsOnlyDirective {
  private static readonly allowedKeyCodes = [
    "Backspace",
    "Delete",
    "Insert",
    "ArrowUp",
    "ArrowRight",
    "ArrowDown",
    "ArrowLeft",
    "Tab",
    "Home",
    "End",
    "Enter",
    "Digit1",
    "Digit2",
    "Digit3",
    "Digit4",
    "Digit5",
    "Digit6",
    "Digit7",
    "Digit8",
    "Digit9",
    "Digit0",
    "Numpad0",
    "Numpad1",
    "Numpad2",
    "Numpad3",
    "Numpad4",
    "Numpad5",
    "Numpad6",
    "Numpad7",
    "Numpad8",
    "Numpad9",
  ];

  @HostListener('keydown', ['$event'])
  onKeyDown(e: KeyboardEvent) {
    // This condition checks whether a keyboard control key was pressed.
    // I've left this 'open' on purpose, because I don't want to restrict which commands
    // can be executed in the browser. For example, It wouldn't make sense for me to prevent
    // a find command (Ctrl + F or Command + F) just for having the focus on the input with
    // this directive.
    const isCommandExecution = e.ctrlKey || e.metaKey || e.shiftKey || e.altKey;
    const isKeyAllowed = InputDigitsOnlyDirective.allowedKeyCodes.indexOf(e.code) !== -1;

    if (!isCommandExecution && !isKeyAllowed) {
      e.preventDefault();
      return;  // let it happen, don't do anything
    }
  }
}

那么你只需要在输入中添加指令：

<input type="text" inputDigitsOnly>

您可以更改它以满足您的需要。你可以 check the list of available key codes here.

希望对您有所帮助。

如何限制输入文本框只能以 Angular2 形式输入数字？

How to restrict input textbox to enter numbers only in Angular2 form?

javascript

angular

angular2-template

angular2-forms

angular2-services