Can you explain the concept of "indexing JavaScript objects with strings"?

var people = new Array();
function People (name, location, age){
    this.name = name;
    this.location = location;
    this.age = age;
}

I have two other functions to create and insert people data into a table.

function generatePeople(){}
function loadPeopleIntoTable(){}

My goal is to analyze the list of people and identify the most common first names. This functionality is encapsulated within the commonFirstName() function.

function commonFirstName(){}

The issue I am facing revolves around accessing the 'people' array within the commonFirstName() function. Despite having the code to iterate through the array and find common names, it only seems to work with manually created arrays instead of the 'people' array. Why is that?

The hint suggests that "JavaScript objects can be indexed by strings," but I'm still unclear on its application in this context. Although I've written the code for identifying common first names, I'm unable to utilize the 'people' array within the function.


function commonFirstName(){ 
       alert(people[1]); 
       //Additional logic for determining common names 
 }

When executed, the output displays as [object Object]. However, if I use:

function commonFirstName(){
tempArray = ['John Smith', 'Jane Smith', 'John Black'];
//Logic for finding common names here 
}

An alert message showing "Common Name: John. Occurs 2 times" is generated.

I attempted passing the 'people' array to the function like so:

function commonFirstName(people){
alert(people[1]);
}

This should ideally return some output related to element 1's full name, location, and age, but alas, there's no response at all. It almost feels as though the array is either empty or does not exist.

The entirety of my code is structured below:

(previous code snippet)

At present, while the algorithm successfully identifies common names when using a predefined fullNames array, integrating the 'people' array - which encompasses People objects with name, location, and age properties - remains a challenge. All I require is to pass this array through so I can manipulate the elements accordingly.

Answer №1

In JavaScript, the concept of "JavaScript objects can be indexed by strings" essentially means that an object can be treated like a hash table. Each method or field name is essentially a String key in this table. Rather than accessing properties using dot notation like object.anyName, you can also use bracket notation like object['anyName'].

For the purpose of an exercise, you can utilize this feature to create a counter for commonly used names.

As this is just an exercise, I'll provide a hint rather than a full solution:

  • Iterate through each item in an array and extract the person's name.
  • Use the person's name as a key in a "table". If the name already exists in the table, increment the counter by one.
  • By the end of the operation, you should have pairs of names and their respective occurrences.

If you find the exercise challenging, take a look at the source code of lodash's `countBy` function (https://github.com/lodash/lodash/blob/4.13.1/lodash.js#L8373). It demonstrates how to accomplish this task.

Answer №2

After reviewing your modification: utilizing the array as a parameter functions properly, eliminating the necessity to include the array within the function itself:

var fullNames = ['Alice Green', 'Bob Smith', 'Charlie Brown'];

function mostCommonName(array) {                

            var tempArray = [];
            var firstPart;
            for (i=0; i < array.length; i++){
                firstPart = array[i].split(' ').slice(0, -1).join(' ');
                tempArray.push(firstPart);
            }

            var commonest;
            var frequency = 0;
            for (j=0; j < tempArray.length; j++){
                var currentName = tempArray[j];
                var nameCount = 0;
                for (k=0; k < tempArray.length; k++){
                    if (tempArray[k] == currentName){
                        nameCount++;
                    }
                    if (nameCount > frequency){
                        commonest = currentName;
                        frequency = nameCount;
                    }
                }
            }
            alert(commonest + " : " + frequency);
        }

 mostCommonName(fullNames);

View the demonstration here: https://jsfiddle.net/h8ty3eko/

Answer №3

Everything is resolved as I have identified the issue. It is necessary to access the individual variables inside each object in the People array by calling people[i].name, for instance, rather than just using people[i] on its own.

Your contributions are greatly appreciated :)

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