var toString = require('./toString');

/** Used to generate unique IDs. */ var idCounter = 0;

/**

* Generates a unique ID. If `prefix` is given, the ID is appended to it.
*
* @static
* @since 0.1.0
* @memberOf _
* @category Util
* @param {string} [prefix=''] The value to prefix the ID with.
* @returns {string} Returns the unique ID.
* @example
*
* _.uniqueId('contact_');
* // => 'contact_104'
*
* _.uniqueId();
* // => '105'
*/

function uniqueId(prefix) {

var id = ++idCounter;
return toString(prefix) + id;

}

module.exports = uniqueId;