sequency/lib/singleOrNull.js

Functional sequences for processing iterable data in JavaScript

Object.defineProperty(exports, "__esModule", { value: true });
exports.SingleOrNull = void 0;
var SingleOrNull = /** @class */ (function () {
    function SingleOrNull() {
    }
    /**
     * Returns the single element of the sequence or `null` if the sequence has more than
     * one element or none at all. If a `predicate` is passed returns the single element matching
     * the predicate or `null` if more or less than one element match the predicate.
     *
     * @param {(value: T) => boolean} predicate
     * @returns {T}
     */
    SingleOrNull.prototype.singleOrNull = function (predicate) {
        if (predicate != null) {
            return this.filter(predicate).singleOrNull();
        }
        var first = this.iterator.next();
        if (first.done) {
            return null;
        }
        if (!this.iterator.next().done) {
            return null;
        }
        return first.value;
    };
    return SingleOrNull;
}());
exports.SingleOrNull = SingleOrNull;
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