vscode-extension-samples/quickinput-sample/src/basicInput.ts

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

import { window } from 'vscode';

/**
 * Shows an input box using window.showInputBox().
 */
export async function showInputBox() {
	const result = await window.showInputBox({
		value: 'abcdef',
		valueSelection: [2, 4],
		placeHolder: 'For example: fedcba. But not: 123',
		validateInput: text => Promise.resolve(text === '123' ? 'Not 123!' : null)
	});
	window.showInformationMessage(`Got: ${result}`);
}