Tiny JS utility to print duration in a human readable fashion

readable-duration.js

/* Author: Didrik Nordström, didrik@betamos.se */

/**
 * Format a duration in milliseconds to a human readable format, e.g.
 * "4y 2d 3h 10m 10s 255ms". Negative durations are formatted like "- 8h 30s".
 * Granularity is always ms.
 *
 * @param t Duration in milliseconds
 * @return A formatted string containing the duration or "" if t=0
 */
var readableDuration = (function() {

	// Each unit is an object with a suffix s and divisor d
	var units = [
		{s: 'ms', d: 1},
		{s: 's', d: 1000},
		{s: 'm', d: 60},
		{s: 'h', d: 60},
		{s: 'd', d: 24},
		{s: 'y', d: 365} // final unit
	];

	// Closure function
	return function(t) {
		t = parseInt(t); // In order to use modulus
		var trunc, n = Math.abs(t), i, out = []; // out: list of strings to concat
		for (i = 0; i < units.length; i++) {
			n = Math.floor(n / units[i].d); // Total number of this unit
			// Truncate e.g. 26h to 2h using modulus with next unit divisor
			trunc = (i+1 < units.length) ? n % units[i+1].d : n; // …if not final unit
			trunc ? out.unshift(''+ trunc + units[i].s) : null; // Output if non-zero
		}
		(t < 0) ? out.unshift('-') : null; // Handle negative durations
		return out.join(' ');
	};
})();