Is there a way in JavaScript to determine if an array contains two or more identical values?
For instance;
['one','two','three'] -> false, because no items in the array are repeated.
['one','one','two'] -> true, because 'one' appears multiple times.
['one','one','one','two'] -> true, because 'one' appears multiple times.
['askja', 'askja', 'askja', 'iamms']Appreciate your help.
Here are several methods to achieve this task:
1: Follow the method proposed by Stevens Qiu. By comparing the length of the array with the Set, you can identify if there is a repeat in the array. This method is highly recommended.
2: Another way is to iterate through the array, adding each value to a hash during each iteration. If the value already exists in the hash, it indicates a repeat, returning true.
3: Alternatively, you can iterate through the array, obtaining the index of the item (indexOf()) and the last index of the item (lastIndex()) during each iteration. If these values are not equal, it suggests that there is a repeat in the array.
const arr = ['hi', 'bye', 'hi'];
const arr2 = ['hi', 'bye', 'what'];
// Set size < arr length, so returns false
console.log(arr.length === new Set(arr).size);
// Set size == arr length, so returns true
console.log(arr2.length === new Set(arr2).size);To check for duplicate values in an array, loop through the elements and add them to a Set data structure. If the size of the Set does not change after adding an element, it means there are duplicates in the array.
An effective approach involves creating a map that keeps track of the presence (i.e., true if exists) of item values based on their keys.
Once an item is identified to already exist in the map, it indicates the occurrence of multiple duplicates of a string in the input array:
function checkForDuplicates(arr) {
/*
A temporary map used to mark the presence of a key in arr
*/
const map = {};
for(const item of arr) {
if(map[item]) {
/*
If the map contains the key/value pair for the item, it means the item appears at least twice in arr
*/
return true;
}
map[item] = true;
}
return false;
}
console.log(checkForDuplicates(['one','two','three']), "=== false")
console.log(checkForDuplicates(['one','one','two']), "=== true")
console.log(checkForDuplicates(['one','one','one','two']), "=== true")This code snippet provides a way to identify unique values in an array, detect duplicates, and check if there are any duplicates present.
const numbers = [];
const uniqueNumbers = [...new Set(numbers)];
const duplicateNumbers = numbers.reduce((acc, num) => {
return uniqueNumbers.includes(num) ? acc : [...acc, num];
}, []);
const hasDuplicates = duplicateNumbers.length > 0;
I'm attempting to design a unique Shiny slider that represents the months of the year. My desired outcome is for the slider to display the names of the months as strings, rather than numeric values where 1 corresponds to January, 2 corresponds to Febr ...
Being a novice developer in Html/Javascript/CSS/Jquery coding, I recently encountered an issue while integrating Jquery into my project. When I imported Jquery, the styling of simple buttons went haywire. Jquery worked perfectly fine when using its classes ...
I needed to adjust the font size of specific text within an option tag in my code snippet below. <select> <?php foreach($dataholder as $key=>$value): ?> <option value='<?php echo $value; ?>' ><?php echo ...
Just starting out with AngularJS and experiencing issues with HTML5 nested form validation. I currently have 2 forms; mainFrm (parent form) and stateFrm (a child form). I am struggling to validate each form within its own scope. <form id="mainFrm" ng- ...
Currently, I am working on a function called onGroundUserClick within the Scope passedScope. The goal is to have a function triggered upon the completion of loading the iframe that will establish ng-click. var $tdName = $("<td/>", { ...
When attempting to create an array called requestData using the input values from a user details form, I encountered an error stating that .val() is not a function. The code snippet where this problem occurred is as follows: Jquery $('#submit' ...
I am new to VueJS and I am facing a challenge converting my VueJS project to use TypeScript. I have been trying to bind functions to certain variables in JavaScript, but I am struggling with accomplishing the same in TypeScript. Even though there are no er ...
I'm in the process of developing a mobile application and I find myself in need of utilizing bip39 for passphrase generation. However, after installing the necessary package, I encountered errors related to missing packages like stream buffer events. ...
Can someone help me with my HTML issue? <a href="/someplace"> <div> <vuecomp></vuecomp> <span>Click row for more info</span> </div> </a> Following is the Vue component I am working on... ...
After storing 10 strings to an array, I loop through a worksheet to add more elements to the array starting at position 10 (11th element), and it works perfectly. arr = Array("Summary", "Account Summary", "Calendarization", "Vehicles", "Buildings", "Perso ...
Within my Express API functionality, I aim to offer the client flexibility in providing their contact details, namely phone number or website address, with the option of leaving them blank. The SELECT queries in use are as follows: -- Retrieve all users S ...
Is it possible for JavaScript to create a sparse array similar to what Bash can do in one line? names=([0]="Bob" [1]="Peter" [20]="$USER" [21]="Big Bad John") § Creating Arrays Can JavaScript achieve the same with sparse arrays? ...
I am currently working on a solution using protractor where I have several options to consider. Specifically, I need to test timeslots between 1600 and 1900, along with an else statement. For instance, if the 1600 timeslot is selected, then the code shoul ...
AngularJS 2 is on the horizon, and the documentation recommends three languages: Typescript, Javascript, and Dart. As someone who primarily works with Javascript EcmaScript 5, I'm curious about the strengths and weaknesses of these three options. Cu ...
In the past, I encountered a challenge with the $http service which I managed to solve by creating a dedicated service for handling my requests. However, as my requests grew larger, this solution started to seem inefficient. Instead of just assigning a sim ...
I have created a Javascript-based navigation bar that is triggered by clicks instead of hover for better mobile usability. I have made sure to keep the HTML, CSS, and JavaScript code as simple as possible. To ensure that clicking anywhere outside the menu ...
I've experimented with various approaches to inserting my array into my PHPmyAdmin Database via localhost, but none have yielded successful results thus far. It seems like I might be complicating things by incorporating too many different solutions at ...
My objective is to obtain the complete index of a complex object within a multidimensional array. For example, consider the following array: var arr = [ { name: "zero", children: null }, { name: "one", children: [ { ...
Having an issue while attempting to use a forEach loop in ejs to render HTML on the page. Below is the code snippet for the store page with the ejs forEach loop. <% include _includes/header.ejs %> <div class="container"> <% cards.fo ...
Currently, I am facing an issue when trying to read XML files. Strangely, the code works flawlessly on my personal computer running OS X. However, when I run the same code on a DigitalOcean Ubuntu 16 Server, it fails to produce any results. I am utilizing ...