Simple method which fills out the placeholders in a string

format-string.js

/**
 * Formats a string and replaces the placeholders.
 *
 * @example format('<div class="%0"'>%1</div>, [value for %0], [value for %1], ...)
 *
 * @param {String} str
 * @param {Mixed}
 * @returns {String}
 */
var format = function (str) {
    for (var i = 1; i < arguments.length; i++) {
        str = str.replace('%' + (i - 1), arguments[i]);
    }
    return str;
};