sprintf for JavaScript

format.js

/**
 *
 */
String.prototype.format = function formatString(...subs) {

	// String tag functions
	// @ref https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals
	const formatter = (strings, ...keys) => {

		return (...values) => {

			let dict = values[values.length - 1] || {}
			let res = [strings[0] || '']

			keys.forEach((key, i) => {

				let val = Number.isInteger(key) ? values[key] : dict[key]
				res.push(val, strings[i + 1])
			})

			return res.join('')
		}
	}

	// Dispatch a dynamic built function
	// What a joke JavaScript ...
	return Function('f', '...x', 'return f`' + this + '`(...x)').call(null, formatter, ...subs)
}

// Ex.
// let fmt = 'Hello ${0}!'
// let s0 = fmt.format('world')
// let s1 = fmt.format(1024)