| import { Operator } from '../Operator'; |
| import { Subscriber } from '../Subscriber'; |
| import { Observable } from '../Observable'; |
| import { OperatorFunction } from '../types'; |
| |
| /** |
| * Applies a given `project` function to each value emitted by the source |
| * Observable, and emits the resulting values as an Observable. |
| * |
| * <span class="informal">Like [Array.prototype.map()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map), |
| * it passes each source value through a transformation function to get |
| * corresponding output values.</span> |
| * |
| * ![](map.png) |
| * |
| * Similar to the well known `Array.prototype.map` function, this operator |
| * applies a projection to each value and emits that projection in the output |
| * Observable. |
| * |
| * ## Example |
| * Map every click to the clientX position of that click |
| * ```ts |
| * import { fromEvent } from 'rxjs'; |
| * import { map } from 'rxjs/operators'; |
| * |
| * const clicks = fromEvent(document, 'click'); |
| * const positions = clicks.pipe(map(ev => ev.clientX)); |
| * positions.subscribe(x => console.log(x)); |
| * ``` |
| * |
| * @see {@link mapTo} |
| * @see {@link pluck} |
| * |
| * @param {function(value: T, index: number): R} project The function to apply |
| * to each `value` emitted by the source Observable. The `index` parameter is |
| * the number `i` for the i-th emission that has happened since the |
| * subscription, starting from the number `0`. |
| * @param {any} [thisArg] An optional argument to define what `this` is in the |
| * `project` function. |
| * @return {Observable<R>} An Observable that emits the values from the source |
| * Observable transformed by the given `project` function. |
| * @method map |
| * @owner Observable |
| */ |
| export function map<T, R>(project: (value: T, index: number) => R, thisArg?: any): OperatorFunction<T, R> { |
| return function mapOperation(source: Observable<T>): Observable<R> { |
| if (typeof project !== 'function') { |
| throw new TypeError('argument is not a function. Are you looking for `mapTo()`?'); |
| } |
| return source.lift(new MapOperator(project, thisArg)); |
| }; |
| } |
| |
| export class MapOperator<T, R> implements Operator<T, R> { |
| constructor(private project: (value: T, index: number) => R, private thisArg: any) { |
| } |
| |
| call(subscriber: Subscriber<R>, source: any): any { |
| return source.subscribe(new MapSubscriber(subscriber, this.project, this.thisArg)); |
| } |
| } |
| |
| /** |
| * We need this JSDoc comment for affecting ESDoc. |
| * @ignore |
| * @extends {Ignored} |
| */ |
| class MapSubscriber<T, R> extends Subscriber<T> { |
| count: number = 0; |
| private thisArg: any; |
| |
| constructor(destination: Subscriber<R>, |
| private project: (value: T, index: number) => R, |
| thisArg: any) { |
| super(destination); |
| this.thisArg = thisArg || this; |
| } |
| |
| // NOTE: This looks unoptimized, but it's actually purposefully NOT |
| // using try/catch optimizations. |
| protected _next(value: T) { |
| let result: any; |
| try { |
| result = this.project.call(this.thisArg, value, this.count++); |
| } catch (err) { |
| this.destination.error(err); |
| return; |
| } |
| this.destination.next(result); |
| } |
| } |