javascript - 如何选择任何数量并更改其值？

Question

我是 ionic 3 的新手，想了解代码请帮助我。我想选择任何项目，它的值得到的更改小计可能会反射(reflect)到它的输出。

cart.ts

private _values1 = [" 1 ", "2", " 3 "," 4 "," 5 "," 6 "];

  firstDropDownChanged(_values1: any) 
  {
    this.currentPrice = (parseInt(this.product.subtotal) * this._values1);
    console.log(this.currentPrice);
    this.product.subtotal =this.currentPrice;
    console.log(this.product._values1);
  }

cart.html

  <span style="font-size: 14px !important;">Qty:</span>   
  <select class="sel" (change)="firstDropDownChanged()">
  <option *ngFor='let v of _values1'>{{ v }}</option>
  </select>

Answer 1

您可以使用 [(ngModel)] 作为 2 向数据绑定(bind)

<select class="sel" (change)="firstDropDownChanged()" [(ngModel)]="selectedValue">
        <option *ngFor='let v of _values1' [ngValue]="v">{{ v }}</option>
 </select>

因此，每次更改选项时，所选选项的当前值将在 selectedValue 变量中。在 .ts 文件中用作

firstDropDownChanged() {
   this.currentPrice = this.product.subtotal * this.selectedValue;
    console.log(this.currentPrice);
    this.product.subtotal =this.currentPrice;
  }

Stackblitz Demo using ngModel