By using the Javascript Array Length property can get the numbers of elements in an Array. A Lenght property returns the number of elements in that array. The length of the Array can be stored in a JavaScript variable.
Now, you might be thinking what is the use of Array Length?
Javascript array length is mainly used in loop statements. Let’s assume you have data of fruits’ names in an array and want to show these fruits as a list to users. For that, you need to run a loop on Array, where the loop will break if all array elements (fruits) counts are finished.
A Syntax of getting the length of an array.
array.lengthA Syntax of Setting the Length of an Array.
array.length = numberIt is a useful tool for manipulating and iterating over arrays in JavaScript. This property can be accessed and modified using built-in array methods, allowing developers to easily add or remove elements from an array
Javascript gets array length Example
Let’s see a simple example of How JavaScript checks array length.
On Clicking a button “myFunction()” function will call. In a function, the first script will create an array and assign value to the count variable. And in last show this value in a p element.
<!DOCTYPE html>
<html>
<body>
<button onclick="myFunction()">Click and get array length</button>
<p id="demo"></p>
<script>
function myFunction() {
var fruits = ["Apple", "Orange", "Kiwi", "Mango"];
var count = fruits.length;
document.getElementById("demo").innerHTML = count;
}
</script>
</body>
</html>
Output: 4
Javascript array length 0
or How do I empty an array in JavaScript?
For example, this is an array:-
arr = [1,2,3,4];How can I empty that?
Let’s see the ways to clear an existing array:
Method 1
This code will set the array variable “arr” to a new empty array. It will be perfect if you don’t have references to the original array.
arr = [];Method 2
By setting the array length to zero.
arr.length = 0Method 3
Using .splice(), the .splice() function will return an array with all the removed items.
arr.splice(0,arr.length)Method 4
Using the While loop statement and pop() method.
while(arr.length > 0) {
arr.pop();Source: https://stackoverflow.com/questions/1232040/how-do-i-empty-an-array-in-javascript
Difference between Array.length = 0 and Array =[]?
array = [] creates a new array and assigns a reference to it to a variable. Where any other references are unaffected (not changed) but still point to the original array.
array.length = 0 modifies the array itself. If it accesses via a different array variable, then it will get the modified array.
Source: https://stackoverflow.com/questions/4804235/difference-between-array-length-0-and-array
Difference between Javascript array length vs size
Array.size() is not a valid method and is not available, always use the length property.
.size() is in jQuery and many other libraries.
.length work only when a
.length work well for this type of array
Question: How to initialize an array’s length in javascript?
Answer: You can create an Array with size but not suggested and Theoretically there is no need for this. Here is the code and print the length in the console.
var arr = new Array(5);
console.log(arr.length) // 5Question: How to a JavaScript array cut length?
Answer: Method 1
You can cut or limit the length of an array in JavaScript by using a using splice() function.
arr.slice(0,5)Complete code example
In the example changing the original array values.
<!DOCTYPE html>
<html>
<body>
<button onclick="myFunction()">Click and get array length</button>
<p id="demo"></p>
<script>
function myFunction() {
var fruits = ["Apple", "Orange", "Kiwi", "Mango"];
var citrus = fruits.slice(1, 3);
var count = citrus.length;
document.getElementById("demo").innerHTML = count;
}
</script>
</body>
</html>Method 2
Another option to cut length is by setting .length
arr.length =2;Complete code
The new array is created in this example.
<!DOCTYPE html>
<html>
<body>
<button onclick="myFunction()">Click and get array length</button>
<p id="demo"></p>
<script>
function myFunction() {
var fruits = ["Apple", "Orange", "Kiwi", "Mango"];
fruits.length =2;
document.getElementById("demo").innerHTML = fruits.length;
}
</script>
</body>
</html>
Output: 2 (for both examples)
Do comment if you have any doubts or suggestions on this tutorial.
Note: The All JavaScript check array length Examples are tested on Safari browser (Version 12.0.2).
OS: macOS 10.14 Mojave
Code: HTML 5 Version