Obtain data from a [closed] chain

You can:

var cadena = "13msi2";
    var cadenaSeparada = cadena.split("");
    for (i = 0; i < cadenaSeparada.length; i++) { 
    	alert(cadenaSeparada[i]);
	}

You can review the w3schools example: link

A small modification for your example: link

var cadena = "13msi2";
var cadenaSeparada = cadena.split("");
for (var i in cadenaSeparada) {
    document.write(cadenaSeparada[i]);
    document.write("<br/>");
}

// Output: 
// 1
// 3
// m
// s
// i
// 2

The substr () method returns the characters of a string that start at a specified location and according to the number of characters that are specified.

Example: Using substr

var cadena = "abcdefghij";

console.log("(1,2): "    + cadena.substr(1,2));   // '(1, 2): bc'
console.log("(-3,2): "   + cadena.substr(-3,2));  // '(-3, 2): hi'
console.log("(-3): "     + cadena.substr(-3));    // '(-3): hij'
console.log("(1): "      + cadena.substr(1));     // '(1): bcdefghij'
console.log("(-20, 2): " + cadena.substr(-20,2)); // '(-20, 2): ab'
console.log("(20, 2): "  + cadena.substr(20,2));  // '(20, 2): '

This script shows:

(1,2): bc (-3,2): hi (-3): hij (1): bcdefghij (-20, 2): ab (20, 2):

If you are using jQuery you can do the following:

$(document).ready(function(){
	var cadena = "13msi2";
	var array = cadena.split("");

	$.each(array,function(i){
	   alert(array[i]);
	});

});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>