Angular valuechanges call multiple times while Page loading

I am using angular 4 and i am checking is any value is changed by user or not? In my page there are more than 100 control(textbox ,dropdown and editable grid)

I need to check only if any value is changed or not. For that i am using below code but it is called multiple times while pageload.

How i can avoid this.i need valuechange will execute only on when user change any value.


import { Component, OnInit, ViewChild, AfterViewInit, HostListener, OnChanges, DoCheck, AfterViewChecked,OnDestroy } from "@angular/core";


@ViewChild('fromNote') fnotes;

ngAfterViewInit() {
this.fnotes.valueChanges.subscribe(val => {
alert('changed');
});
}

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