Using JavaScript to Get the Max Value in an Array

In JavaScript, to get the max value in an array we can do this by using a for loop with an if conditional statement. Here is a function to get the max number of an array.

function getMaxNum(){
  var maxNumber = arrayOfNumber[0];
  for (var i = 0; i < arrayOfNumber.length; i++) {
    if( arrayOfNumber[i] > maxNumber ){
      maxNumber = arrayOfNumber[i];
    }
  }
  return maxNumber;
}

Let’s see an example of this function below.

In the example below, we will have an array of numbers. We will use our getMaxNum() function we created above to find the maximum number and return it.

var numbersArray = [4,3,5,8,14,67,56,23];

function getMaxNum(){
  var maxNumber = numbersArray[0];
  for (var i = 0; i < numbersArray.length; i++) {
    if( numbersArray[i] > maxNumber ){
      maxNumber = numbersArray[i];
    }
  }
  return maxNumber;
}

var maxNum = getMaxNum(numbersArray);

The variable maxNum above would have value 67.

Interactive Example of Getting the Max Value of an Array

Below we will provide code to let the user input as many numbers as they want separated by a comma(,).

Here is the simple HTML set up:

<p>Type as many numbers as you want separated by a comma.</p>
<p>If the numbers are not separated by a comma only, this example will not work.</p>
<input id="userArr" type="text" placeholder="1,2,3">
<div id="click-me" onclick="getMaxNum()">Get Max Number</div>
<div id="results"></div>

We will then create an array of numbers from this input and find the max value using the getMaxNum() function we created above.

To create an array from the string of numbers the user provides, we will use the split() method along with the Array map() method. We will add this code to our getMaxNum function.

We will update the results below using the textContent property..

function getMaxNum(){
  
  //Get the user input
  var userInput = document.getElementById("userArr").value;

  //Convert user input to an array of numbers
  var numbersArray = userInput.split(',').map(Number);

  //Find the max number
  var maxNumber = numbersArray[0];
  for (var i = 0; i < numbersArray.length; i++) {
    if( numbersArray[i] > maxNumber ){
      maxNumber = numbersArray[i];
    }
  }

  //Display the max number
  document.getElementById("results").textContent = "The max number is: " + maxNumber;

}

The final code and output for this example is below:

Code Output:

Full Code:

<p>Type as many numbers as you want separated by a comma.</p>
<p>If the numbers are not separated by a comma only, this example will not work.</p>
<input id="userArr" type="text" placeholder="1,2,3">
<div id="click-me" onclick="getMaxNum()">Get Max Number</div>
<div id="results"></div>

<script>

function getMaxNum(){
  var userInput = document.getElementById("userArr").value;
  var numbersArray = userInput.split(',').map(Number);
  var maxNumber = numbersArray[0];
  for (var i = 0; i < numbersArray.length; i++) {
    if( numbersArray[i] > maxNumber ){
      maxNumber = numbersArray[i];
    }
  }
  document.getElementById("results").textContent = "The max number is: " + maxNumber;
}

</script>

Hopefully this article has helped you to understand how to get the max value in an array using JavaScript.