Angular: Check string contains substring using JavaScript

Hi,

In my site I have a search box for cities and right now i have to search for whole word such as "New York", but I want to be able to search with portion of the word such as "New" or "York", how to do that?

here is my code:

html:

<label>Filter City:</label>
<input [(ngModel)]='City'>
<button type="button" (click)="onCityFilter()">Search</button>
<button type="button" (click)="onCityFilterClear()">Clear</button>

in ts:

City ='';
SearchCity = '';
onCityFilter(){
    this.SearchCity = this.City;
}
onCityFilterClear(){
    this.SearchCity = '';
    this.City = '';
}

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
    name: 'filter'
})
export class FilterPipe implements PipeTransform {
  transform(value: any[], filterString: string, propName: string): any[] {
    const resultArray = [];

    if (value.length === 0 || filterString === '' || propName === ''){
      return value;
    }

    for (const item of value){
      if (item[propName].toLocaleLowerCase() === filterString.toLocaleLowerCase()) {     
        resultArray.push(item);
      }
    }

    return resultArray;    
  }
}