Look for duplicate values in an array, retrieve the value, and determine the frequency

I've populated an array with a random number of strings.

var array = ["car", "plane", "plane", "car", "car"];

I want to access the values in the Array and count how many times each one has been added. For example:

var a = "car";
var aCount = 3;
var b = "plane";
var bCount = 2;

var text = "'" + a + "'" + " was found " + aCount + " times";
return text

I'm not sure how to use a loop to compare array[i] with all other values in the array, especially since the length of the array is random?

Thank you.

javascriptarrays

Answer №1

Transform the array values into keys and start tallying!

let valueCount = {};
for (let index = 0; index < values.length; index++) {
    if (valueCount.hasOwnProperty(values[index])) {
        valueCount[values[index]]++;
    } else {
        valueCount[values[index]] = 1;
    }
}

The object valueCount now stores the count of each array value.

Example: http://jsfiddle.net/oe0x6dbg/

Answer №2

To achieve this, you can utilize the Array.reduce method: 

var items = ["apple", "banana", "banana", "apple", "apple"];

var result = items.reduce(function(counts, item) {
                 counts[item] = (counts[item] || 0) + 1;
                 return counts;
             }, {});

for(var key in result) {
    console.log('\'' + key + '\' appeared ' + result[key] + ' times');
}

/*
    Result:
    --------
    { 'apple': 3, 'banana': 2 }

    Console Output:
    ----------------
    'apple' appeared 3 times
    'banana' appeared 2 times
*/

Answer №3

You have the power to make it happen

let myArray = someArray.join();
let finalResult = {};

for (let index = 0; index < someArray.length; index++) {
    finalResult[someArray[index]] = myArray.match(new RegExp(someArray[index], "g")).length;
    myArray.replace(new RegExp(someArray[index], "g"), "");
}

console.log(finalResult); // {bike: 2, skateboard: 1}

Answer №4

An easy fix might involve introducing a "counter" variable as shown below:

var array = ["dog", "cat", "cat", "dog", "dog"];

var counter = {};

// Assign each element in the array to a key in the object
for (var i = 0; i < array.length; i++) {
    if (typeof counter[array[i]] === 'undefined') {
        counter[array[i]] = 1;
    } else {
        counter[array[i]]++;
    }
}

// Iterate through the object and display the counts
for (var item in counter) {
    console.log("'" + item + "'" + " appeared " + counter[item] + " times");
}

JSFiddle Link

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