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How to create dynamic length array with numbers and sum the numbers using JavaScript ?

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  • Last Updated : 16 Jan, 2023
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In JavaScript, array is a single variable that is used to store different elements. It is often used when we want to store a list of elements and access them by a single variable. Unlike most languages where the array is a reference to the multiple variables, in JavaScript array is a single variable that stores multiple elements.

JavaScript Arrays are Dynamic in nature which means, the length of the array can be modified at run time (when necessary). Array length can be specified after declaring the array as shown in the following example.

Example: This example shows the declaration of an array with length 10.

Javascript




// Declare an array of undefined size
var arr = [];
  
// Set array length to 10
arr.length = 10;
  
// Print the length to console
console.log(arr);

Output: 

Array(10) [ <10 empty slots> ]

Example: As you can see, this method explains the array with 10 empty slots. The following example declares an array and takes input elements using a prompt dynamically and prints the sum of all elements and displays the result using an alert.

Javascript




(function () {
      
    // Declare an array of undefined size
    var arr = [];
  
    // Notice how the size of array
    // is not dot defined
  
    // Initiating loop to iterate
    // for inputs
    for (var i = 0; i < 10; i++) { 
  
        // Feeding integer inputs to array
        arr[i] = +prompt('Enter number');
          
        // Calculate sum of array elements
        var sum = arr.reduce(function (a, b) {
            return a + b;
        }, 0)
    }
    alert(sum);
})();

Output:

Input : 1 2 3 4 5 6 7 8 9 10
Output :55


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