util.js

/**
 * DIY browser shim for node's `util`
 *
 * @package www
 * @author Derek Reynolds <drk@diy.org>
 */

// NOTE: These type checking functions intentionally don't use `instanceof`
// because it is fragile and can be easily faked with `Object.create()`.
function isArray (ar) {
    if (typeof Array.isArray === 'function') return Array.isArray(ar);

    return Object.prototype.toString.call(ar) === '[object Array]';
}

function isBoolean (arg) {
    return typeof arg === 'boolean';
}

function isFunction (arg) {
    return typeof arg === 'function';
}

function isObject (arg) {
    return typeof arg === 'object' && arg;
}

function isNull (arg) {
    return arg === null;
}

function isNumber (arg) {
    return typeof arg === 'number';
}

function isString (arg) {
    return typeof arg === 'string';
}

function isUndefined (arg) {
    return arg === void 0;
}

/**
 * util.format browser shim
 *
 * First param is string to format and any other arguments will 
 * be used as replacements within the format string.
 *
 * @param {string} f - String to format
 */
function format (f) {
    var i;

    if (!isString(f)) {
        return; // noop
    }

    i = 1;
    var args = arguments;
    var len = args.length;
    var str = String(f).replace(/%[sdj%]/g, function(x) {
        if (x === '%%') return '%';
        if (i >= len) return x;
        switch (x) {
            case '%s': return String(args[i++]);
            case '%d': return Number(args[i++]);
            case '%j':
                try {
                    return JSON.stringify(args[i++]);
                } catch (_) {
                    return '[Circular]';
                }
                break;
            default:
                return x;
        }
    });

    for (var x = args[i]; i < len; x = args[++i]) {
        if (isNull(x) || !isObject(x)) {
            str += ' ' + x;
        } else {
            str += ' '; // noop
        }
    }

    return str;
}

/**
 * Exports
 */
module.exports = {
    format: format,
    inherits: require('inherits'),
    isBoolean: isBoolean,
    isArray: isArray,
    isFunction: isFunction,
    isObject: isObject,
    isNull: isNull,
    isNumber: isNumber,
    isString: isString,
    isUndefined: isUndefined
};