A repr function for JS

repr.js

'use strict';
/* Python-like repr() formatter for JS types, with recursion limit. */
/* Adapted from https://gist.github.com/soapie/6407618 */
function repr(x, max, depth) {
	var ELIDED = "[..]";
	if (depth === undefined) depth = 0;
	if (max === undefined) max = 2;
	if (isPrim(x))
		return showPrim(x);
	if (typeof x === 'function')
		return 'function';
	if (Array.isArray(x))
		return showArray(x, depth, max);
	if (x.constructor === Object)
		return showObj(x, depth, max);
	if (x.constructor === String)
		return showPrim(x.toString());
	return x.toString();

	function isPrim(x) {
		return x === null || /^[snbu]/.test(typeof x)
	}
	function showPrim(x) {
		var t = typeof x;
		if (t === 'string')
			return JSON.stringify(x);
		if (t === 'number' || t === 'boolean')
			return x.toString();
		if (x === null)
			return 'null';
		if (t === 'undefined')
			return 'undefined';
	}
	function showArray(arr, depth, max) {
		if (depth >= max) return ELIDED;
		var i, r = '[';
		// for loop instead of forEach to correctly handle sparse arrays
		for (i = 0; i < arr.length; i += 1) {
			if (i !== 0) r += ', ';
			// check if arr[i] is undefined... there's a distinction between
			// arr[i] being set to undefined and not being set at all
			if (arr.hasOwnProperty(i.toString())) {
				r += repr(arr[i], depth + 1, max);
			}
		}
		return r + ']'
	}
	function showObj(o, depth, max) {
		if (depth >= max) return ELIDED;
		var r = '{';
		Object.keys(o).forEach(function (key, ix) {
			if (ix !== 0) r += ', ';
			r += key + ': ' + repr(o[key], depth + 1, max);
		})
		return r + '}'
	}
}