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@reactivex/ix-esnext-esm

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The Interactive Extensions for JavaScript

github.com/ReactiveX/IxJS

ReactiveX/IxJS

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/** * Returns the first element in a sequence that satisfies a specified condition if provided, else * the first element in the sequence. * @param {Iterable<T>} source Source collection * @param {function:(value: T): boolean} [selector] An optional function to test each element for a condition. * @returns {T | undefined} The first element in the sequence that passes the test in the * specified predicate function if provided, else the first element. If there are no elements, * undefined is returned. */ export declare function first<T, S extends T>(source: Iterable<T>, predicate: (value: T, index: number) => value is S): S | undefined; export declare function first<T>(source: Iterable<T>, predicate?: (value: T, index: number) => boolean): T | undefined;