What is the exact functioning of the Array.push() method in Javascript?

During my online CS class, we covered the topic of how Arrays and memory work. The teacher used C as an example to explain that you cannot add extra elements to a full Array. As someone who started with JavaScript, I found it interesting that in JavaScript, the Array.push() function allows for adding elements easily. However, this concept seemed different from what I had learned in regards to Arrays. Curious, I turned to Google and StackOverflow but couldn't find a clear answer on why JavaScript can do this.

Does JavaScript create a new Array with added elements and point the variable to the new Array, or is there another explanation?

javascriptarrays

Answer №1

When comparing arrays in JavaScript to arrays in C, there are significant differences. In C, you must allocate a new array with a specific type and size, and if you need to adjust the size, you have to create a new array altogether. However, JavaScript arrays work differently. According to the MDN documentation on arrays, JavaScript arrays are list-like objects that allow for easy resizing and storage of any data type.

Arrays in JavaScript can change in length at any time, and elements can be stored at non-contiguous locations within the array. This flexibility sets JavaScript arrays apart from traditional fixed-size arrays.

Despite being called "arrays," they function more like lists in JavaScript, offering freedom in resizing and storing any data type due to the language's dynamic nature.

If you're curious about how the push/pop methods work internally in JavaScript arrays, this Stack Overflow thread provides insightful information.

Answer №2

Contrary to a C array, a JavaScript Array behaves more like a C++ std::vector. It dynamically expands its length by allocating memory as required.

The documentation for std::vector explains this behavior:

Vectors typically occupy more space compared to static arrays as they allocate additional memory to accommodate future growth. This strategy eliminates the need for frequent reallocations when inserting elements, and only triggers reallocation once the allocated memory is exhausted. Consequently, reallocations can be performance-intensive operations.

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