How to select mat checkbox, mat select based on the data - json

Question

I have a set of mat checkboxes and mat selects that gets populated based on values from a config file. Once these components are created on the page they need to get selected based on the data associated with the user displayed.I have written functions to make them selected based on the data, but don't see them working as expected. Here is my code:
html:
<table class="table">
<tr class="node-width" *ngFor="let element of configArray">
<mat-checkbox color="primary" name="element.type" [checked]="isCheckboxChecked(element.type)"
(change)="getCheckBoxvalue($event, element)">{{element.type}}
</mat-checkbox>
<mat-select placeholder="Select Sub Type" name="subtype" [formControl]="subtypes"
(selectionChange)="getSelectValue($event.value, element)" multiple>
<mat-option *ngFor="let subtype of element.subtypes" [value]="subtype"
[selected]="isOptionSelected(element.type, subtype)">
{{subtype}}
</mat-option>
</mat-select>
</tr>
</table>
typescript:
isCheckboxChecked(elementtype: string): boolean {
this.getTypesForTheCurrentApplication.forEach((item) => {
if (item.element === elementtype) {
this.checked = true;
} else {
this.checked = false;
}
});
this.changeDetector.markForCheck();
return this.checked;
}
isOptionSelected(elementtype: string, subtype: string): boolean {
this.getTypesForTheCurrentApplication.forEach((item) => {
if (item.element === elementtype) {
item.subtypes.forEach((element) => {
if (element === subtype) {
this.selected = true;
} else {
this.selected = false;
}
});
}
});
this.changeDetector.markForCheck();
return this.selected;
}
The function named 'getTypesForTheCurrentApplication' is called to query the back end db to get the json array values for the data displayed. Any help is greatly appreciated.
Thanks.