how to count characters in string in js code example

Example 1: javascript string lentrh

var myString = "string test";
var stringLength = myString.length;

console.log(stringLength); // Will return 11 because myString 
// 							  is 11 characters long...

Example 2: how to count specific letters in string js

console.log(("str1,str2,str3,str4".match(/,/g) || []).length); //logs 3

console.log(("str1,str2,str3,str4".match(new RegExp("str", "g")) || []).length); //logs 4

Example 3: count value a to b character javascript

function count (string) {  
  var count = {};
  string.split('').forEach(function(s) {
     count[s] ? count[s]++ : count[s] = 1;
  });
  return count;
}