"use strict";
var distinctUntilChanged_1 = require('./distinctUntilChanged');
/**
 * Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from the previous item,
 * using a property accessed by using the key provided to check if the two items are distinct.
 * If a comparator function is provided, then it will be called for each item to test for whether or not that value should be emitted.
 * If a comparator function is not provided, an equality check is used by default.
 * @param {string} key string key for object property lookup on each item.
 * @param {function} [compare] optional comparison function called to test if an item is distinct from the previous item in the source.
 * @return {Observable} an Observable that emits items from the source Observable with distinct values based on the key specified.
 * @method distinctUntilKeyChanged
 * @owner Observable
 */
function distinctUntilKeyChanged(key, compare) {
    return distinctUntilChanged_1.distinctUntilChanged.call(this, function (x, y) {
        if (compare) {
            return compare(x[key], y[key]);
        }
        return x[key] === y[key];
    });
}
exports.distinctUntilKeyChanged = distinctUntilKeyChanged;
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