Generate random alphanumeric string in JavaScript

random-string.js

// @source: http://stackoverflow.com/questions/1349404/generate-a-string-of-5-random-characters-in-javascript

function randomStr(m) {
	var m = m || 9; s = '', r = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
	for (var i=0; i < m; i++) { s += r.charAt(Math.floor(Math.random()*r.length)); }
	return s;
};

try this npm i random-key-generator

why variables s and r are global?
another solution for this task: http://javascript-benchmark.info/t/generate-random-string