角度-在输入更改时进行服务调用

你能做什么:

1. 当元素聚焦时,保存当前值
2. 当元素失去焦点时,将当前值与保存的值进行比较
3. 如果值已更改,则执行处理

<input (focus)="saveValue()" (blur)="processChange()" [(ngModel)]="someValue" ... />

someValue = "nice";
prevValue = this.someValue;

saveValue() {
  this.prevValue = this.someValue;
}

processChange() {
  if (this.someValue !== this.prevValue) {
    console.log("The value has changed!!!");
    // Do some additional processing...
  }
}

看到了吗 this stackblitz

如果不想更改组件代码,请将值保存在元素的属性中:

<input #txt type="text" name="field" 
  (focus)="txt.setAttribute('data-value', someValue)" 
  (blur)="txt.getAttribute('data-value') !== someValue ? processChange() : ''" 
  [(ngModel)]="someValue" />

看到了吗 this stackblitz