javascript random alphanumeric string

1Math.random().toString(36).substr(2, 6); //6 is the length of the string

1var characters = 'abcdefghijklmnopqrstuvwxyz0123456789';
2var result = ""
3var charactersLength = characters.length;
4
5for ( var i = 0; i < 5 ; i++ ) {
6    result += characters.charAt(Math.floor(Math.random() * charactersLength));
7}
8
9console.log(result)

1// n is an integer
2function randomString (n) {
3    // create array of length n filled with null
4    let tmpArr = Array.apply(null, Array(n));
5    
6    // for each index generate a random positive integer
7    // less than 36 and convert it to a base 36 digit
8    tmpArr.map((v, i) =>
9        Math.floor(Math.random() * 36).toString(36)
10    ).join('');
11
12    return tmpArr;
13}