Angular 2: Enable button when form is updated - for-loop

Question

I want to enable a button if at least one field in the form is updated, but when I input some changes in my textarea, the button remains disabled.
I have 3 items in my form - Input Field, Multiple Select Dropdown, Textarea
The button enables when there are changes in the input field or multiple select dropdown, but when I change something in the textarea, it won't enable. Maybe there's something wrong with the for loop and the breaks
Here are my codes:
if (this.data.process == "update") {
for(const f in this.categoryForm.value){
console.log(this.categoryForm.value);
if (f == "categorytags"){
let categorytagsArray = [];
let categorytagsFormArray = this.categoryForm.value[f];
for (const x in this.data.category[f]) {
categorytagsArray.push(this.data.category[f][x]._id);
}
if (categorytagsArray.length != categorytagsFormArray.length) {
this.disableButton = false;
break;
} else {
for (const i in categorytagsFormArray) {
if (categorytagsArray.indexOf(categorytagsFormArray[i]) == -1) {
this.disableButton = false;
break;
} else {
this.disableButton = true;
}
}
}
break;
}
else {
if (this.categoryForm.value[f] == this.data.category[f]) {
this.disableButton = true;
} else {
this.disableButton = false;
break;
}
}
}
}
<div class="dialog-form">
<div class="header">{{data.title}}</div>
<div class="content">
<form class="ui form" [formGroup]="categoryForm" *ngIf="categoryForm" novalidate>
<div class="field required" [class.error]="formErrors.name">
<label>Name</label>
<input type="text" formControlName="name" placeholder="Enter Name..." maxlength="100">
<div *ngIf="formErrors.name" class="field-error">
{{ formErrors.name }}
</div>
</div>
<div class="field required" [class.error]="formErrors.categorytags">
<label>Category Tag</label>
<select name="categorytags" id="categorytags" class="ui fluid dropdown" formControlName="categorytags" multiple="">
<option [attr.value]=categoryTag._id *ngFor="let categoryTag of categorytags">{{ categoryTag.name }}</option>
</select>
<div *ngIf="formErrors.categorytags" class="field-error">
{{ formErrors.categorytags }}
</div>
</div>
<div class="field">
<label>Remarks</label>
<textarea rows="6" formControlName="remark" maxlength="1000"></textarea>
</div>
</form>
</div>
<div class="actions">
<button class="ui basic button" (click)="cancel()">Cancel</button>
<button class="ui primary button" [disabled]="disableButton" (click)="save()">{{data.process.charAt(0).toUpperCase() + data.process.slice(1)}}</button>
</div>
</div>