Angular 2：如何防止表单在按键输入时提交？

Question

我有一个表单，其中一个字段充当自动完成功能。如果用户输入一个单词并按下回车，则该字段的内容应添加到该字段下方的列表中。

问题：当用户点击回车时，自然是整个表单都被提交了。

我已经在处理按键的函数上return false。但是表单似乎在调用这个函数之前就已经提交了。

如何防止这种情况发生？

基本形式：

<div id="profileForm">
  <form [formGroup]="profileForm" (ngSubmit)="onSubmit()" method="post" *ngIf="!showSuccessMessage">

    <div class="row">

      <div class="form-group col-xs-12 col-sm-6">
        <label for="first_name">My Skills</label>
        <div class="autocomplete">
          <input formControlName="skill_string" [(ngModel)]="skillString" name="skill_string"
          type="text" class="form-control" id="skill_string" placeholder="Comma separated" (keyup.enter)="skillsHandleEnter(skillString)">
          <ul class="autocomplete-list" *ngIf="skillHints.length > 0">
            <li class="list-item" *ngFor="let skill of skillHints" (click)="addSkillFromAutocomplete(skill)">{{skill}}</li>
          </ul>
        </div>
        <div id="skill-cloud" class="tag-cloud">
          <span class="skill-tag tag label label-success" *ngFor="let skill of selectedSkills" (click)="removeSkill(skill)">{{skill}} x</span>
        </div>
      </div>

    </div>

    <div class="row">

      <hr>

      <div class="form-group submit-group">
        <div class="col-sm-12">
          <button type="submit" class="btn btn-primary pull-right" [disabled]="!profileForm.valid">Save</button>
        </div>
      </div>

    </div>

  </form>
</div>

基本组件（我剥离了很多在这里发布的逻辑）：

import { Component, OnInit } from '@angular/core';
import { FormGroup, FormBuilder } from '@angular/forms';
import { ActivatedRoute, Router } from '@angular/router';

import { Subscription } from 'rxjs/Rx';
import 'rxjs/add/operator/debounceTime';
import * as _ from 'lodash';

import { MemberService } from '../shared/index';

@Component({
  moduleId: module.id,
  selector: 'signup',
  templateUrl: 'signup.component.html',
  styleUrls: ['signup.component.css']
})
export class SignupComponent implements OnInit {

  private profileForm:FormGroup;
  private validation_errors:Array<any>;
  private selectedSkills:Array<string>;
  private skillHints:Array<string>;
  private skillString:string;

  constructor(private route: ActivatedRoute,
    private formBuilder: FormBuilder,
    private memberService: MemberService,
    private router: Router ) {

      this.selectedSkills = [];
      this.skillHints = [];
      this.skillString = '';

      // Set up form
      this.profileForm = this.formBuilder.group({
        skill_string: ['']
      });

  }

  ngOnInit(): any {
    // Do something
  }



  updateSelectedSkills(skillString:string):void {
    if(skillString) ) {
      let cleanString = skillString.trim().replace(/[ ]{2,}/g, ' ');
      this.selectedSkills = _.compact(this.selectedSkills.concat(cleanString.split(',')));
      this.skillString = '';
      this.skillHints = [];
    }
  }

  skillsHandleEnter(skillString:string):void {
    console.log("ENTER");
    this.updateSelectedSkills(skillString);
    return false;
  }

  autocompleteSkills(term:string):void {
    this.memberService.autocompleteSkills(term).subscribe(
      res => {
        this.skillHints = [];
        for(let i = 0; i < res.data.length; i++) {
          this.skillHints.push(res.data[i].name);
        }
      }
    );
  }

  addSkillFromAutocomplete(skillString:string):void {
    this.selectedSkills.push(skillString);
    this.memberProfile.skill_string = '';
    this.skillHints = [];
    this.skillString = '';
  }


  onSubmit():void {
    this.memberService.saveProfile(this.memberProfile, this.selectedSkills).subscribe(
      res => {
        console.log(res);
      }
    );
  }

}

Answer 1

所以答案实际上很简单...不是Event.preventDefault()，因为我在输入字段上听 Enter 而不是按钮。从button 中删除type="submit" 是不够的，因为默认情况下所有按钮都是类型提交。唯一需要更改的是按钮元素，显式添加type="button" 并添加(click) 侦听器：

<button type="button" (click)="onSubmit()" class="btn btn-primary pull-right" [disabled]="!profileForm.valid">Save</button>

唯一的问题：现在用 enter 提交表单永远不会工作。只在焦点位于自动完成输入字段时阻止 enter 提交表单会更优雅一点。

编辑：

只有在光标在自动完成字段时才阻止enter提交表单可以通过使用Ankit Singh的解决方案并稍作修改来实现：

<form [formGroup]="profileForm" (ngSubmit)="onSubmit()" method="post" (keydown.enter)="$event.target.id != 'skill_string'" *ngIf="!showSuccessMessage">

（注意：条件必须返回false以防止触发默认动作）

当然，我们需要再次使用常规的提交按钮（不附加点击事件，否则表单将提交两次）：

<button type="submit" class="btn btn-primary pull-right" [disabled]="!profileForm.valid">Save</button>

如果您想使用.autocomplete 类，也可以检查event.target.classList。或者将检查逻辑移至您将$event 传递到其中的函数。

Answer 2

试试

<form (keydown.enter)="$event.target.tagName == 'TEXTAREA'" [formGroup]="profileForm" (ngSubmit)="onSubmit($event)">

它还将允许enter 在Textareas 中。

Answer 3

Angular 2 中的事件表现得像普通的 DOM 事件。要捕获事件对象，请在模板的事件回调中将$event 作为参数传递：

HTML：

<button (keyup.enter)="skillsHandleEnter($event, skillString)"></button>

JavaScript 使用 Event.preventDefault():

@Component(...)
class MyComponent {
  skillsHandleEnter(event, skillString) {
    event.preventDefault();
    // ... your logic
  }
}

Answer 4

通过 enter 或单击 button

阻止表单提交

<textarea (keydown.enter)="provoked($event)"></textarea>

<button (keydown.enter)="provoked($event)" (click)="provoked($event)"></button>

provoked($event) {
   $event.preventDefault()
}

如果您需要将数据传递给方法，请尝试

<textarea (keydown.enter)="provoked($event, data)"></textarea>

<button (keydown.enter)="provoked($event, data)" (click)="provoked($event, data)"></button>

provoked($event, data) {
   $event.preventDefault()

   // process the data here
}