The following example illustrates this behavior. It sounds like the data structure is confusing :-) If you have an object with unknown/random property names, you can't really access a specific property without knowing the name. You could use a computed property The syntax to access an array member By default the indexing of every JavaScript array starts from 0. If your code needs to create arrays with single elements of an arbitrary data type, it is safer to use array … As we saw, arrays can have several dimensions, which means that an array element can contain an array, whose elements can contain arrays, etc. It would help to know what your AJAX request looks like. Calling Array(N) results in a RangeError, if N is a non-whole number whose fractional portion is non-zero. Remember that the index values start at 0, not 1. This means that array indexes start at 0 and go up to the number of elements, minus 1. I recommend using $.ajax() and specifying the dataType as JSON, or using $.getJSON(). – Strille Oct 3 '13 at 9:04 An “indexed” array is one where the index must be an integer, and you access its elements using its index as a reference. We can loop through the entirety of the array with the for keyword, taking advantage of the length property. JavaScript for loops iterate over each item in an array. Here’s an example of an indexed array: Here’s an example of … An array can hold many values under a single name, and you can access the values by referring to an index number. The Basic For Loop. As we can see data is an object, hence we can access its properties using dot notation. let arr = Array (9.3) // RangeError: Invalid array length. The items property is accessed as follows: data.items The value is an array, to access its second element, we have to use bracket notation: data.items[1] This value is an object and we use dot notation again to access the name property. Here is an example that demonstrates $.ajax() and shows you how to access the returned values in an array. Referencing items in arrays is done with a numeric index, starting at zero and ending with the array length minus 1. So, our array of four elements has indexes from 0 to 3. Looping Through an Array. I ask because when you find yourself trying to circumvent one of the most basic characteristics of a programming language, odds are good there's a better way to do what you're trying to do. So we eventually get: In the above example, we removed seahorse from the array, and pushed a new value into index 3. The problem most likely is that the value is undefined at some point in the components lifecycle (you're probably loading it asynchronously). Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube. You are going to need be be defensive in the way that you reference your property. 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