**** 2019 Answer ****

This single line will do the trick:

Array.from(String(12345), Number);

Example

const numToSeparate = 12345;

const arrayOfDigits = Array.from(String(numToSeparate), Number);

console.log(arrayOfDigits);   //[1,2,3,4,5]

Explanation

1- String(numToSeparate) will convert the number 12345 into a string, returning '12345'

2- The Array.from() method creates a new Array instance from an array-like or iterable object, the string '12345' is an iterable object, so it will create an Array from it.

3- In the process of creating this new array, the Array.from() method will first pass any iterable element (ex: '1', '2') to the callback we declare as a second parameter (which is the Number function in this case). This is possible because an String is an "array-like" object. To make it simpler, we could've declared the callback as: Array.from(String(numToSeparate), n => Number(n)

4- The Number function will take any string character and will convert it into a number eg: Number('1'); will return 1.

5- These numbers will be added one by one to a new array and finally this array of numbers will be returned.

Summary

The code line Array.from(String(numToSeparate), Number); will convert the number into a string, take each character of that string, convert it into a number and put in a new array. Finally, this new array of numbers will be returned.

I'd do this, to avoid using strings when you don't need them:

var n = 12345;
var arr = [];
while(n>0){arr.unshift(n%10);n=n/10|0;}

var n = 12345;
var arr = ('' + n).split('').map(function(digit)  {return +digit;});

The map function, though, is only supported by recent browsers.

Another way is by using literals and then spread:

const n = 12345;
const arr = [...`${n}`].map(Number);
console.log(arr);

date: 24/07/2021

Using ES6 methods #2021

input = 12345

output = [1,2,3,4,5]

const input = 12345;
console.log(`${input}`.split('').map(Number));

Without to string solution.

This method is faster than method with toString transform. Approximately 3-4 times. You can see benchmarks here or on screen below.

const numberToArray = (number) => {
    var arr = [];
    while(number>0) { arr.push(number%10); number = number/10|0; }
    return arr.reverse();
}

Use Map(Number). Below code snip can helpful.

 var num = 1230945;
 var result=num.toString().split('').map(Number);
 console.log(result);

I hope I am not too late to the party, but...

If you are code golfing, then do

const n = 9876
const a = [...""+n].map(n=>+n) // 20 chars
console.log(a)

Explanation:

• ""+ converts n into a string to concatenate it with the "" part
• ... is the spread syntax. It expands the string ""+n into an array
• the + before n in map just converts back every array element from string to number

The rest should be clear. Cheers!

I have fist convert the number to a string and then used Array.from() to convert the string to an array.

let dataArray = Array.from(value.toString());

Runnable snippet:

const n = 12345;
let toIntArray = (n) => ([...n + ""].map(Number));
console.log(toIntArray(n));

First, the integer is converted string & then to array. Using map function, individual strings are converted to numbers with the help of parseInt function. Finally, that array is returned as the result.

const digitize = n => [...`${n}`].map(i => parseInt(i));

The solutions proposed work fine in most cases but not with negative numbers.

There is a solution for such cases.

const intToArray = (int) => {
  return String(int).match(/-?\d/g).map(Number)
}

console.log(intToArray(312)) // [3, 1, 2]
console.log(intToArray(-312)) // [-3, 1, 2]

You can use inbuilt JS methods toString() and parseInt() as:

function toDigitsArr(num) {
  num = num.toString();
  let numArr = [];
  for (let i = 0; i < num.length; i++) {
    numArr[i] = parseInt(num[i]);
  }
  return numArr;
}
console.log(toDigitsArr(9119));

You can do something like this

let n = 12345;
let arr = (""+n).split('');//HERE IS THE ARRAY
///Now for, for loop, you can do something like this
arr.map(element=>{
//Do Something
})

You guys are awesome, so many ways to do the trick. Let me put this one into consideration. Please provide feedback if there is something wrong with this approach.

    let fromNumberToArray = [...num.toString()].map(Number);

You can just use the String() method. It coverts to string but you can use them in term of digits.

But if you want the data as array of string

let val = 1458;
let numbers = String(val);
console.log("First response => ",numbers);
let fromNumberToArray = [...val.toString()].map(Number);
console.log("Second response => ",fromNumberToArray)

This is a very simple way using basic javascript that makes sense:

function toNumArray(num) {
     num = num.toString();
      let numArr = []
      for (let i = 0; i < num.length; i++) {
        numArr.push(num[i])
      }
      return numArr;
    }
 console.log(toNumArray(911956789874))

don't forget the case where the number is negative

function toArr2(num) {
  var myArr = String(Math.abs(num)).split("").map((num)=>{
  return Number(num)})

  if (num <0) myArr[0]*=-1;
  
return myArr;
}

console.log(toArr2(123));
console.log(toArr2(-123));

var n = 12345;

var s = String(n).split('').map(Number);

console.log(s);

Depending on the scenario, you might wish to only wrap it with bracelets: [myNumber]

E.g:

const myNumber = element.Id;
methodThatReceivesAnArray([myNumber]);