string-utils.js

/**
 * @fileoverview Utilities to operate on strings.
 * @author Stephen Wade
 */

"use strict";

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------

// eslint-disable-next-line no-control-regex -- intentionally including control characters
const ASCII_REGEX = /^[\u0000-\u007f]*$/u;

/** @type {Intl.Segmenter | undefined} */
let segmenter;

//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------

/**
 * Converts the first letter of a string to uppercase.
 * @param {string} string The string to operate on
 * @returns {string} The converted string
 */
function upperCaseFirst(string) {
	if (string.length <= 1) {
		return string.toUpperCase();
	}
	return string[0].toUpperCase() + string.slice(1);
}

/**
 * Counts graphemes in a given string.
 * @param {string} value A string to count graphemes.
 * @returns {number} The number of graphemes in `value`.
 */
function getGraphemeCount(value) {
	if (ASCII_REGEX.test(value)) {
		return value.length;
	}

	segmenter ??= new Intl.Segmenter("en-US"); // en-US locale should be supported everywhere
	let graphemeCount = 0;

	// eslint-disable-next-line no-unused-vars -- for-of needs a variable
	for (const unused of segmenter.segment(value)) {
		graphemeCount++;
	}

	return graphemeCount;
}

module.exports = {
	upperCaseFirst,
	getGraphemeCount,
};