检查几个值是否以反应形式发生了变化

Question

I have some fields in reactive forms that I have to check if values have changed. I know how to check if value have changed on one field like this

this.form.controls['phone'].valueChanges.subscribe(
  data => console.log('form changes', data)
  );

The problem I have is that I need to check two or more fields, eg phone and address.

Answer 1

You can merge observables, but it merges into a single observable, ie

import { merge } from 'rxjs';

merge(
  this.form.controls['phone'].valueChanges,
  this.form.controls['address'].valueChanges
).subscribe(console.log)

alternatively you can use combineLatest. Which will emit the latest value from each observable. I think this is what you need.

import { combineLatest } from 'rxjs';

combineLatest(
  this.form.controls['phone'].valueChanges, 
  this.form.controls['address'].valueChanges
).subscribe((phone, address) => {
  // do something
})