/**
 * Assigns (shallow copies) the properties of `src` onto `dest`, if the
 * corresponding property on `dest` === `undefined`.
 *
 * @param {Object} dest The destination object.
 * @param {Object} src The source object.
 * @return {Object} The destination object (`dest`)
 */
export declare function defaults(dest: any, src: any): any;
/**
 * Truncates the `str` at `len - ellipsisChars.length`, and adds the `ellipsisChars` to the
 * end of the string (by default, two periods: '..'). If the `str` length does not exceed
 * `len`, the string will be returned unchanged.
 *
 * @param {String} str The string to truncate and add an ellipsis to.
 * @param {Number} truncateLen The length to truncate the string at.
 * @param {String} [ellipsisChars=...] The ellipsis character(s) to add to the end of `str`
 *   when truncated. Defaults to '...'
 */
export declare function ellipsis(str: string, truncateLen: number, ellipsisChars?: string): string;
/**
 * Supports `Array.prototype.indexOf()` functionality for old IE (IE8 and below).
 *
 * @param {Array} arr The array to find an element of.
 * @param {*} element The element to find in the array, and return the index of.
 * @return {Number} The index of the `element`, or -1 if it was not found.
 */
export declare function indexOf<T>(arr: T[], element: T): number;
/**
 * Removes array elements based on a filtering function. Mutates the input
 * array.
 *
 * Using this instead of the ES5 Array.prototype.filter() function, to allow
 * Autolinker compatibility with IE8, and also to prevent creating many new
 * arrays in memory for filtering.
 *
 * @param {Array} arr The array to remove elements from. This array is
 *   mutated.
 * @param {Function} fn A function which should return `true` to
 *   remove an element.
 * @return {Array} The mutated input `arr`.
 */
export declare function remove<T>(arr: T[], fn: (item: T) => boolean): void;
/**
 * Performs the functionality of what modern browsers do when `String.prototype.split()` is called
 * with a regular expression that contains capturing parenthesis.
 *
 * For example:
 *
 *     // Modern browsers:
 *     "a,b,c".split( /(,)/ );  // --> [ 'a', ',', 'b', ',', 'c' ]
 *
 *     // Old IE (including IE8):
 *     "a,b,c".split( /(,)/ );  // --> [ 'a', 'b', 'c' ]
 *
 * This method emulates the functionality of modern browsers for the old IE case.
 *
 * @param {String} str The string to split.
 * @param {RegExp} splitRegex The regular expression to split the input `str` on. The splitting
 *   character(s) will be spliced into the array, as in the "modern browsers" example in the
 *   description of this method.
 *   Note #1: the supplied regular expression **must** have the 'g' flag specified.
 *   Note #2: for simplicity's sake, the regular expression does not need
 *   to contain capturing parenthesis - it will be assumed that any match has them.
 * @return {String[]} The split array of strings, with the splitting character(s) included.
 */
export declare function splitAndCapture(str: string, splitRegex: RegExp): string[];
/**
 * Function that should never be called but is used to check that every
 * enum value is handled using TypeScript's 'never' type.
 */
export declare function throwUnhandledCaseError(theValue: never): void;