JavaScript generates m-digit random numbers based on time, with a maximum of 13 digits_javascript skills

Generate m-digit random number based on time, with a maximum of 13-digit random number, and there is no guarantee that the first bit is not 0

function ran(m) {
m = m > 13 ? 13 : m;
var num = new Date().getTime();
return num.toString().substring(13 - m);
}
console.log(ran(5));

According to the random number generated by Math's random function, m digits are intercepted. The generated random number does not exceed 16 digits at most, and the first bit is guaranteed not to be 0

function rand(m) {
m = m > 16 ? 16 : m;
var num = Math.random().toString();
if(num.substr(num.length - m, 1) === '0') {
return rand(m);
}
return num.substring(num.length - m);
}
console.log(rand(5));

Generated based on Math’s random function, there is no limit on the number of digits, and the first bit is not 0

function rando(m) {
var num = '';
for(var i = 0; i < m; i++) {
var val = parseInt(Math.random()*10, 10);
if(i === 0 && val === 0) {
i--;
continue;
}
num += val;
}
return num;
}
console.log(rando(5));