JavaScript concept with a cup of coffee and a laptop

Arrays – Multiple values in one

Arrays are variables that allow us to store multiple values in a single item. For example, if you collect baseball cards, you might have a cards array and your individual baseball cards in each slot of the array.

How do we create an array? In JavaScript, we use square brackets to denote an array. Here is the creation of an empty array.

let baseballCards = [ ];

To initialize the array with data, we separate each item with a comma…

let baseballCards = [ ‘Aaron’, ‘Ruth’, ‘Wagner’ ];

To access each value within an array, we can use what is called subscripting. It looks like this…

console.log( baseballCards[1] );

The number in the brackets is the index position of the item in the array. The aforementioned line of code will output the value “Ruth”. That may seem odd because when you look at the array, “Ruth” is in the second position, not the first. Arrays are zero-based. This means they start counting at zero. If we replace the index of ‘1’ with ‘0’ as follows…

console.log( baseballCards[1] );

“Aaron” will output to the console. If you attempt to access an item that does not exist, it will output undefined. Our example array has three items (0, 1, 2 for Aaron, Ruth, Wagner). If we try the following line of code…

console.log( baseballCards[3] );

It will report as undefined.

Happy Coding!

Clay Hess

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