javascript Check if an array is empty or exists

If the array’s length is greater than zero it contains at least 1 element. Knowing how to check for an empty array is an important coding skill which can often come in handy.

• That is, we can use it to return true if an array is empty.
• The nested if can be avoided using &&, as in image_array && image_array.length, it will short circuit if image_array doesn’t exist.
• Then the more risky check of array.length, which could error us if array is undefined, can be checked.
• In my case, array_.length always returned 0, even if it had values inside.
• If you have to support the browser, use the next approach in this article.
• To check if the array is empty or not with .length, we can do this in in three ways.

If the length of the array is 0, then the array is empty otherwise it is not empty. If you are new to programming or quite unfamiliar with javascript, we recommend you read through the entire article, as each section of the article would be useful. But if i remove image_array from the else everything works just fine.

Demonstration of checking if the array is empty using Javascript

It can be helpful in a situation where you have to show or hide something on a web page depending on whether the array is empty or not. Learn more on JavaScript, functional programming, and front-end development. We can see here that fruitArr is an array and hence passes into the second condition to check if the length of the array is empty. In my case, array_.length always returned 0, even if it had values inside. This means we can’t guarantee what type of object a variable holds. There is a chance that we’re not talking to an instance of Array. When checking if an array is empty or not, it’s often best to also check if the array is indeed an array.

• These properties can then be used together with the AND(&&) operator to determine whether the array exists and is not empty.
• True, but length property can return that the variable is empty even for non-array variables so we need to ensure that we are dealing with an array first before using the length property.
• Create a function that check the size of the array and pass the lenght by parameter.
• Let’s use this with an if statement, and print out a message if our array is empty.
• When you’re programming in JavaScript, you might need to know how to check whether an array is empty or not.
• This means that they have different built-in objects (i.e. different global objects, different constructors, etc.).
• Undefined variable is a variable that you haven’t assigned anything to it yet.

We check if the current element’s value is equal to an empty string and returntrue if it is. We use theArray.includesmethod to check if the array contains an empty string. Here, since the array is empty, the function returns True. If the length of the object is 0, then the array is considered to be empty and the function will return TRUE.

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If our array is empty, the above message will get logged. If the array has elements in it, the code within the if block will not run. The length property sets or returns the number of elements in an array. By knowing the number of elements in the array, you can tell if it is empty or not. We first check if the arr variable stores an array and then check if the array’s length is greater than 0.

The problem is that image_array in the else fires all time. If an array exists – it just overrides it, but alert doesn’t work.

Browser Support

You can check my fiddle here with shows most possible ways to check array. For example a variable is null when you missed or failed to retrieve some data. Undefined variable is a variable that you haven’t assigned anything to it yet. When the page is loading for the first time, I need to check if there is an image in image_array and load the last image. Let’s use this with an if statement, and print out a message if our array is empty.

The first step is to know if the variable’s type is array type or not. If the function returns true at least once, the some method short-circuits and also returns true. The function we pass to theArray.somemethod gets called with each element in the array until it returns true, or iterates over the entire array. The some method returns true if the provided function returns true at least once. You can think of the optional chaining operator as a safe way to access properties.

How to check if an array is empty using Javascript?

If it encounters an undefined or null value it just short-circuits and returns undefined, instead of throwing an error. If we had not used the “not” operator, arr.length would have returned 0. With the operator added, it will return true if its operand is false. On each iteration, check if the current element is equal to an empty string and return true if the condition is met.

The answer is NO, because an array in JavaScript is an instance of the Array object and typeof would return the type object for it. Checking for length of undefined array may throw exception. In this article, we learned that you can use the length property in JavaScript in various ways to check if an array is empty or not. The length property returns the number of items in an array. Because the length property can be used on other data types, it is good to also check that your array is indeed an array as you were expecting. That is, we can use it to return true if an array is empty.

How to check if value exists in an array using Javascript?

Photo by the authorThis short post shows how to check the size of an array and verify if it is not empty. True, but length property can return that the variable is empty even for non-array variables so we need to ensure that we are dealing with an array first before using the length property.

• For me the best way to do it is to put a very broad check before checking for length.
• The reason the length property is not used on its own is because length can apply to different types of values in JavaScript and be valid.
• Array.isArray() will be False and so the variable will go to the else condition.
• The if block will only run if the array’s length is greater than 0.