Create a random token in Javascript based on user details

Question

I want to create a random string (token) which can be used to identify a user whilst avoiding any potential conflicts with any other users\' tokens.

What I was thinking

Answer 1

//length: defines the length of characters to express in the string

const rand=()=>Math.random(0).toString(36).substr(2);
const token=(length)=>(rand()+rand()+rand()+rand()).substr(0,length);

console.log(token(40));
//example1:  token(10) => result: tsywlmdqu6
//example2:  token(40) => result: m4vni14mtln2547gy54ksclhcv0dj6tp9fhs1k10