Blog

JavaScript Function that Takes in a String and Outputs an Object Literal that Counts Characters
Posted on June 24, 2015 in Algorithms, JavaScript by Matt Jennings

function countChar(string) {
  
  // Create an empty object
  var countCharObj = {};
  
  // For loop to iterate over a string
  for(var i = 0; i < string.length; i++) {
    
    /*
    If the "countCharObj" does NOT have a property from
    the "string" that is being iterated on
    create a new "countCharObj" property with 
    property name from the iterated "string" and
    set the property's value to 1
    */
    if(!countCharObj.hasOwnProperty(string[i])) {
      countCharObj[string[i]] = 1;
    }  
    else {
    /*  
    If an "countCharObj" property already exists then
    AND has a value of 1 then increment it's value
    */
      countCharObj[string[i]]++;
    }
  }
  
  return countCharObj;
}

var myString = "mycoolstring";

/*
Output of the code below is properties of the "countCharObj" object:
  c: 1,
  g: 1,
  i: 1,
  l: 1,
  m: 1,
  n: 1,
  o: 2,
  r: 1,
  s: 1,
  t: 1,
  y: 1
*/
console.log(countChar(myString));