string-manipulation

function vowelsCount(str){
	var vowels = 'aeiou';
	var evalStr = str.toLowerCase();
	var sum = 0;

	if(evalStr === undefined || evalStr === ''){		//if undefined and or otherwise empty, retun sum default value of 0
		return sum;
	}else{
		var obj = {};	
														//creates empty object to house string values
		for (var i =0; i < evalStr.length; i +=1){		//iterates through string

			if(obj[evalStr[i]]){						
				obj[evalStr[i]] += 1;					//adds 1 if string already has a key of that value
			}else{
				obj[evalStr[i]] = 1;					//creates value as key if not already in object
			}

		}
	
		for(var k in obj){								//looks at every key in object
			if(obj.hasOwnProperty(k)){					//safely inspects those keys with property values
				for (var j = 0; j < vowels.length; j += 1){
					if(vowels[j]===k){							//if the key exists in vowels (see line 2),then add the value to sum
						sum += obj[k];	
					}
				}
			}
		}
		return sum;										//return sum
	}
											
}