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下面的代碼是下拉菜單中的OnChange事件下拉菜單。 $ event.target.value給我的只有新值(這是選擇後)。如何使用onChanges事件獲取以前的值(選擇前的值)。如何從angular2中的下拉菜單中獲取新值和新值
<select class="form-control selectpicker selector" name="selectedQuestion1" [ngModel]="selectedQuestion1" (Onchange)="filterSecurityQuestions($event.target.value,0)">
<option [value]="0" disabled selected>Select Secuirty Question1</option>
<option *ngFor="let securityQuestion of securityQuestions[0]" [value]="securityQuestion.SecurityQuestionID" >
{{securityQuestion.Question}}
</option>
</select> <br />
<div>
<input type="text" class="form-control" id="first_name" name="securityAnswer1" placeholder="Your first security answer">
</div>
filterSecurityQuestions(questionNo: number, securityQtnDropdownNo: number) {
// I want previous value of dropdown here.
}
您可以同時使用點擊事件存儲前值和改變作用於變化。 –