Javascript – Remove Duplicates from Array

Javascript – Remove Duplicates from Array

javascript remove duplicates from the array. In this tutorial, we will explain how to remove duplicate elements or values from an array in javascript.

javascript remove duplicates from the array. In this tutorial, we will explain how to remove duplicate elements or values from an array in javascript.

Here, we will demonstrate to you, many ways or methods to remove duplicate elements or values from a string or numeric array in javascript with examples.

JavaScript Methods: Remove Duplicates From Array Javascript

This tutorial demonstrates easy ways for you. To remove the duplicates from array in javascript.

1. First Way – Set Object

You can use a set object to remove duplicate from an array in javascript.

Syntax

new Set([value]);

Note:– Value – If the parameter is not specified or null is passed
then a new set created is empty.

Ex1:- Using the Set Object Method

We have a number array in javascript, and it has duplicate elements in it. You can use the set object to remove duplicate numbers from array in javascript. You can see the below example:

var number = [1, 2, 1, 3, 4, 5, 2, 6, 3, 4];
 
var unique = [...new Set(number)];
 
document.write( "Output :- " + unique ); 
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>javascript remove duplicate numbers from array</title>
</head>
<body>
  <script type = "text/javascript">
     
    var number = [1, 2, 1, 3, 4, 5, 2, 6, 3, 4];
 
    var unique = [...new Set(number)];
   
    document.write( "Output :- " + unique ); 
 
  </script>  
</body>
</html>

Result of the above code is: Output :- 1,2,3,4,5,6

2. Second Way – filter() function

You can use the javascript filter() and indexof() method to remove duplicates elements or values from array in javascript.

Syntax of filter method:

array.filter(function(currentValue, index, arr), thisValue)

Ex1:- Using the Array.filter() method

var number = [1, 2, 1, 3, 4, 5, 2, 6, 3, 4];
 
var x = (number) => number.filter((v,i) => number.indexOf(v) === i)
 
document.write( "Output :- " + x(number) ); 
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>javascript remove duplicate elements or values from array using filter() function</title>
</head>
<body>
  <script type = "text/javascript">
     
    var number = [1, 2, 1, 3, 4, 5, 2, 6, 3, 4];
 
    var x = (number) => number.filter((v,i) => number.indexOf(v) === i)
   
    document.write( "Output :- " + x(number) ); 
 
  </script>  
</body>
</html>

Result of the above code is: Output :- 1,2,3,4,5,6

Ex2:- Using javascript filter method()

We have an array with duplicate values in javascript. And if you want to remove duplicate elements or values from string array in javascript. So you can use the below example:

var array = ['John','Make','Mac', 'David', 'Smith', 'John', 'Mac', 'Make']
var filterArray = array.filter(function(item, index){
     return array.indexOf(item) >= index;
 });
 
 document.write( "Output :- " + filterArray ); 
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>JavaScript Remove duplicate elements from string array</title>
</head>
<body>
  <script type = "text/javascript">
     
    var array = ['John','Make','Mac', 'David', 'Smith', 'John', 'Mac', 'Make']
    var filterArray = array.filter(function(item, index){
        return array.indexOf(item) >= index;
    });
   
    document.write( "Output :- " + filterArray ); 
 
  </script>  
</body>
</html>

Result of the above code is: Output:- John, Make, Mac, David, Smith

3. Third Way – forEach() Method

You can use the forEach method of javascript to remove duplicates values or elements from array.

Syntax

array.forEach(function(currentValue, index, arr), thisValue);

Ex1:- Using the forEach() method

You can see the example of remove duplicates from array javascript using forEach:

var number = [1, 2, 1, 3, 4, 5, 2, 6, 3, 4];
 
function removeDuplicateFromArray(number) {
  var uniqueVal = {};
  number.forEach(function(i) {
    if(!uniqueVal[i]) {
      uniqueVal[i] = true;
    }
  });
  return Object.keys(uniqueVal);
}
 
document.write( "Output :- " + removeDuplicateFromArray(number) ); 

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Using foreach method of javascript, to remove duplicate elements or values from array</title>
</head>
<body>
  <script type = "text/javascript">
     
    var number = [1, 2, 1, 3, 4, 5, 2, 6, 3, 4];
 
    function removeDuplicateFromArray(number) {
      var uniqueVal = {};
      number.forEach(function(i) {
        if(!uniqueVal[i]) {
          uniqueVal[i] = true;
        }
      });
      return Object.keys(uniqueVal);
    }
   
    document.write( "Output :- " + removeDuplicateFromArray(number) ); 
 
  </script>  
</body>
</html>

Result of the above code is: Output :- 1,2,3,4,5,6

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Understanding Memoization And Dynamic Programming in Javascript

Understanding Memoization And Dynamic Programming in Javascript

In this Javascript tutorial I will explain what memoization is, how to use it, when you should use memoization, how to use memoization, what dynamic programming is, how to use memoization in dynamic programming. Memoization is a big complicated word that you may have never even heard before, but you may be surprised to know that you are most likely already using memoization without even realizing it.

Memoization is a big complicated word that you may have never even heard before, but you may be surprised to know that you are most likely already using memoization without even realizing it. Memoization is just the act of caching values so that they can be calculated quicker in the future. Memoization is really useful in all parts of programming, but where it is most useful is in dynamic programming. In this video I will explain what memoization is, how to use it, and why it is so useful especially in dynamic programming.

🧠 Concepts Covered:

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JavaScript Tutorial: if-else Statement in JavaScript

JavaScript Tutorial: if-else Statement in JavaScript

This JavaScript tutorial is a step by step guide on JavaScript If Else Statements. Learn how to use If Else in javascript and also JavaScript If Else Statements. if-else Statement in JavaScript. JavaScript's conditional statements: if; if-else; nested-if; if-else-if. These statements allow you to control the flow of your program's execution based upon conditions known only during run time.

Decision Making in programming is similar to decision making in real life. In programming also we face some situations where we want a certain block of code to be executed when some condition is fulfilled.
A programming language uses control statements to control the flow of execution of the program based on certain conditions. These are used to cause the flow of execution to advance and branch based on changes to the state of a program.

JavaScript’s conditional statements:

  • if
  • if-else
  • nested-if
  • if-else-if

These statements allow you to control the flow of your program’s execution based upon conditions known only during run time.

  • if: if statement is the most simple decision making statement. It is used to decide whether a certain statement or block of statements will be executed or not i.e if a certain condition is true then a block of statement is executed otherwise not.
    Syntax:
if(condition) 
{
   // Statements to execute if
   // condition is true
}

Here, condition after evaluation will be either true or false. if statement accepts boolean values – if the value is true then it will execute the block of statements under it.
If we do not provide the curly braces ‘{‘ and ‘}’ after if( condition ) then by default if statement will consider the immediate one statement to be inside its block. For example,

if(condition)
   statement1;
   statement2;

// Here if the condition is true, if block 
// will consider only statement1 to be inside 
// its block.

Flow chart:

Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate If statement 

var i = 10; 

if (i > 15) 
document.write("10 is less than 15"); 

// This statement will be executed 
// as if considers one statement by default 
document.write("I am Not in if"); 

< /script> 

Output:

I am Not in if
  • if-else: The if statement alone tells us that if a condition is true it will execute a block of statements and if the condition is false it won’t. But what if we want to do something else if the condition is false. Here comes the else statement. We can use the else statement with if statement to execute a block of code when the condition is false.
    Syntax:
if (condition)
{
    // Executes this block if
    // condition is true
}
else
{
    // Executes this block if
    // condition is false
}


Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate If-else statement 

var i = 10; 

if (i < 15) 
document.write("10 is less than 15"); 
else
document.write("I am Not in if"); 

< /script> 

Output:

i is smaller than 15
  • nested-if A nested if is an if statement that is the target of another if or else. Nested if statements means an if statement inside an if statement. Yes, JavaScript allows us to nest if statements within if statements. i.e, we can place an if statement inside another if statement.
    Syntax:
if (condition1) 
{
   // Executes when condition1 is true
   if (condition2) 
   {
      // Executes when condition2 is true
   }
}

Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate nested-if statement 

var i = 10; 

if (i == 10) { 

// First if statement 
if (i < 15) 
	document.write("i is smaller than 15"); 

// Nested - if statement 
// Will only be executed if statement above 
// it is true 
if (i < 12) 
	document.write("i is smaller than 12 too"); 
else
	document.write("i is greater than 15"); 
} 
< /script> 

Output:

i is smaller than 15
i is smaller than 12 too
  • if-else-if ladder Here, a user can decide among multiple options.The if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.
if (condition)
    statement;
else if (condition)
    statement;
.
.
else
    statement;


Example:

<script type = "text/javaScript"> 
// JavaScript program to illustrate nested-if statement 

var i = 20; 

if (i == 10) 
document.wrte("i is 10"); 
else if (i == 15) 
document.wrte("i is 15"); 
else if (i == 20) 
document.wrte("i is 20"); 
else
document.wrte("i is not present"); 
< /script> 

Output:

i is 20