Angular 如何防止输入中出现退格符号?
我在Angular 2中执行了此指令,以防止输入字段中的退格符号小于3:Angular 如何防止输入中出现退格符号?,angular,Angular,我在Angular 2中执行了此指令,以防止输入字段中的退格符号小于3: import {Directive, ElementRef, HostListener, Input} from '@angular/core'; @Directive({ selector: '[limitTo]' }) export class RestrictInputDirective { @Input() limitTo: number; constructor(private el: Elem
import {Directive, ElementRef, HostListener, Input} from '@angular/core';
@Directive({
selector: '[limitTo]'
})
export class RestrictInputDirective {
@Input() limitTo: number;
constructor(private el: ElementRef) {
}
@HostListener('keydown', ['$event'])
onKeyDown(evt: KeyboardEvent) {
let a = (evt.target as HTMLInputElement).value.length;
if (a <= this.limitTo) {
evt.preventDefault();
}
}
}
import{Directive,ElementRef,HostListener,Input}来自“@angular/core”;
@指示({
选择器:“[Limito]”
})
导出类限制输入指令{
@Input()limito:数字;
构造函数(专用el:ElementRef){
}
@HostListener('keydown',['$event']))
onKeyDown(evt:KeyboardEvent){
设a=(evt.target作为HTMLInputElement).value.length;
如果(a您可以使用keyDown.backspace伪事件来防止退格
@Directive({
selector: '[appLimitTo]'
})
export class LimitToDirective {
@Input('appLimitTo') limitTo: number=5;
constructor(private el: ElementRef) { }
@HostListener('keydown.backspace', ['$event'])
onKeyDown(evt: KeyboardEvent) {
console.log(evt.target.value);
let a = (evt.target as HTMLInputElement).value.length;
if (a <= this.limitTo) {
evt.preventDefault();
}
}
}
@指令({
选择器:“[Applimito]”
})
导出类LimitToDirective{
@输入('Applimito')限制:数字=5;
构造函数(私有el:ElementRef){}
@HostListener('keydown.backspace',['$event']))
onKeyDown(evt:KeyboardEvent){
日志(evt.target.value);
设a=(evt.target作为HTMLInputElement).value.length;
如果(这一行有问题:``console.log(evt.target.value);``将代码更改为console.log(evt.target['value'));如下所示
@Directive({
selector: '[appLimitTo]'
})
export class LimitToDirective {
@Input('appLimitTo') limitTo: number=5;
constructor(private el: ElementRef) { }
@HostListener('keydown.backspace', ['$event'])
onKeyDown(evt: KeyboardEvent) {
console.log(evt.target.value);
let a = (evt.target as HTMLInputElement).value.length;
if (a <= this.limitTo) {
evt.preventDefault();
}
}
}