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JavaScript array.length: Find the Length of an Array
The JavaScript length property is used to find the length of an array. For example:
HTML with JavaScript Code
<!DOCTYPE html>
<html>
<body>
<p id="xyz"></p>
<script>
const cities = ["Tokyo", "Bangkok", "Dubai", "Berlin", "Frankfurt"];
document.getElementById("xyz").innerHTML = cities.length;
</script>
</body>
</html>Output
This code produces an array of city names and assigns it to the cities constant variable.
const cities = ["Tokyo", "Bangkok", "Dubai", "Berlin", "Frankfurt"];
The names of five different cities are contained in the array's five elements.
The dot (.) notation is used to access the array's length property. The "length" property returns the number of array elements. Therefore, through the following JavaScript statement:
document.getElementById("xyz").innerHTML = cities.length;
The value of cities.length is set as the innerHTML property of an HTML element with ID "xyz". Therefore, when the code runs, the number 5 will be displayed inside the "p" tag with ID "xyz". This is because the "length" property returns the number of elements in the cities array, which is 5.
JavaScript length Syntax
The syntax of the length property in JavaScript is:
array.length
The array refers to the array whose length we need to find.
The length of an array represents the total number of items or elements available in the array.
Advantages of the array.length property in JavaScript
- The length property allows you to get the number of elements in an array, which is useful in a variety of situations.
- Elements can be added or removed from an array by changing the length property value. Setting array.length = 0 removes all elements from the array, for example.
- The length property can be utilized in loops to traverse an array by comparing the loop variable to the length property.
Disadvantages of the array.length property in JavaScript
- The length property of sparse arrays may not accurately reflect the number of defined elements in the array. For example, if an array has an element at index 100 but no elements at indices 0-99, the length property will be 101, despite the fact that the array only has two defined elements.
- The length property applies only to arrays and cannot be used to keep track of the size of other types of objects.
- When the length property is set to a value less than its current value, all elements beyond the new length are deleted. For large arrays, this operation can be slow, especially if the new length is close to the old length.
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