azuredatastudio/extensions/mssql/src/util/arrays.ts

/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the Source EULA. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

export function equals<T>(one: ReadonlyArray<T>, other: ReadonlyArray<T>, itemEquals: (a: T, b: T) => boolean = (a, b) => a === b): boolean {
	if (one.length !== other.length) {
		return false;
	}

	for (let i = 0, len = one.length; i < len; i++) {
		if (!itemEquals(one[i], other[i])) {
			return false;
		}
	}

	return true;
}

export function flatten<T>(arr: ReadonlyArray<T>[]): T[] {
	return ([] as T[]).concat.apply([], arr);
}

export function groupBy<T>(data: ReadonlyArray<T>, compare: (a: T, b: T) => number): T[][] {
	const result: T[][] = [];
	let currentGroup: T[] | undefined = undefined;
	for (const element of data.slice(0).sort(compare)) {
		if (!currentGroup || compare(currentGroup[0], element) !== 0) {
			currentGroup = [element];
			result.push(currentGroup);
		} else {
			currentGroup.push(element);
		}
	}
	return result;
}