Take the stress out of picking a bootcamp, Learn web development basics in HTML, CSS, JavaScript by building projects, JavaScript Array Length: A Complete Guide, JavaScript Concat String: A Step-By-Step Guide. We also walked through two examples of the length property. On the final line of our code, we print out a message to the console that states: The average age of a member in the dance class is: , followed by the value stored in the average variable, and a period (.). Read more about this here. If a JavaScript array has four elements, then that array’s “length” property will have a value of “four”. But (and here is the point where many get confused), if a JavaScript array has four elements, the last element has an index of “3”. So, since our array’s “length” property is “5”, our “len” variable is equal to “4”. So, even though the array has a length of 5, the first element has an index of 0, and the last element (the 5th element) has an index of 4. Since length is a property in JavaScript, it does not take in any parameters. The following example uses the Length property to get the total number of elements in an array. Then, we use the Math.round() method to round our value to the nearest integer. Then, we use the length property to find out the length of that list. Receive email notifications about new posts. Our matching algorithm will connect you to job training programs that match your schedule, finances, and skill level. In the below example, we use the length property to find out the length of our array of books we sell that appeared on the New York Times Fiction Best Sellers of 2019 list: When we execute our code, the program returns the following response: 6. This means that JavaScript starts counting from zero when it indexes an array. On the first line, we declare a constant, called nyt_fiction_best_sellers_2019, which stores a list of the books in our inventory that appeared on the New York Times Fiction Best Sellers of 2019 list. So, it follows that if your loop iterates X times, and X equals “one less than” the length of the array, then your loop will always iterate over every element in the array. Gets the total number of elements in all the dimensions of the Array. In this case, there are six values in our list, so the length property returns: 6. Replace the value in the middle by “Classics”. Then, we create a for loop that iterates through each item in the dancer_ages list and adds it to the sum variable. arrays also have a special properties lenght and many function that can manipulate the elements Declaring an array Javascript’s elegance owes a lot to its concise literal syntax for the most common building blocks: object, functions and array.