import {Operator} from '../Operator';
import {Subscriber} from '../Subscriber';
import {tryCatch} from '../util/tryCatch';
import {errorObject} from '../util/errorObject';
import {Observable} from '../Observable';
/**
* Similar to the well-known `Array.prototype.filter` method, this operator filters values down to a set
* allowed by a `select` function
*
* @param {Function} select a function that is used to select the resulting values
* if it returns `true`, the value is emitted, if `false` the value is not passed to the resulting observable
* @param {any} [thisArg] an optional argument to determine the value of `this` in the `select` function
* @returns {Observable} an observable of values allowed by the select function
*/
export function filter<T>(select: (value: T, index: number) => boolean, thisArg?: any): Observable<T> {
return this.lift(new FilterOperator(select, thisArg));
}
class FilterOperator<T> implements Operator<T, T> {
constructor(private select: (value: T, index: number) => boolean, private thisArg?: any) {
}
call(subscriber: Subscriber<T>): Subscriber<T> {
return new FilterSubscriber(subscriber, this.select, this.thisArg);
}
}
class FilterSubscriber<T> extends Subscriber<T> {
count: number = 0;
constructor(destination: Subscriber<T>, private select: (value: T, index: number) => boolean, private thisArg: any) {
super(destination);
this.select = select;
}
protected _next(x: T) {
const result = tryCatch(this.select).call(this.thisArg || this, x, this.count++);
if (result === errorObject) {
this.destination.error(errorObject.e);
} else if (Boolean(result)) {
this.destination.next(x);
}
}
}
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