如何检查ion-textarea的最小长度

Question

如何验证Ionic 3中textarea的最小长度？ Maxlength工作得很好但很奇怪minLength不起作用。

  <ion-textarea id="emailBody" minlength="2"  rows="3" required maxLength="500"  type="text" [(ngModel)]="emailBody"></ion-textarea>

Answer 1

你可以尝试这个解决方案

  

ts文件代码

formObj:any={
        emailBody:""
}

  

html文件代码

<ion-textarea  minlength="2"  rows="3" required maxLength="500"  type="text" [(ngModel)]="formObj.emailBody" #emailBody="ngModel"></ion-textarea>


<div *ngIf="emailBody.invalid && (emailBody.dirty || emailBody.touched)"
     class="alert alert-danger">

  <div *ngIf="emailBody.errors.required">
    emailBody is required.
  </div>
  <div *ngIf="emailBody.errors.minlength">
    emailBody must be at least 2 characters long.
  </div>

</div>

Answer 2

我使用了一些Krishna Rathore和我发现的一些东西。

感谢正确的推动。

  <div class="padding-left-right-10"  *ngIf="!passedEmailTextCheck">
    email text is required.
  </div>

ts文件

if (!passedEmailText) {
   this.passedEmailTextCheck = false;
} else {

// javascript值检查

if( value ) {
}
will evaluate to true if value is not:

null
undefined
NaN
empty string ''
0
false
typescript includes javascript rules.

Answer 3

捕获控件上的输入事件并查看长度

<ion-textarea id="emailBody" minlength="2"  rows="3" required maxLength="500"  type="text" [(ngModel)]="emailBody" (input)="checkLength($event.target.value)"></ion-textarea>

<强> app.component.ts

checkLength(value:any){
   if(value.length<=2){
      //min length found. 
   }
};