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5.4 Adding To Arrays

5.4 Adding To Arrays

JS arrays allow you to directly add to an array without using another type of data structure.

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In Java, you would need an ArrayList. In C++, you would need a vector.

You can add to an Array with the use of the .push(), .unshift(), or .concat() methods.

.push() Example

let fruits = ['apple', 'banana', 'grapes'];
fruits.push('dragon fruit', 'pear');
// fruits = ['apple', 'banana', 'grapes', 'dragon fruit', 'pear'];

Here we see that the .push() adds to the end of the array the new item I put into the method parameter. You could add as many new items as you want.

.unshift() Example

let fruits = ['apple', 'banana', 'grapes'];
fruits.unshift('dragon fruit', 'pear');
// fruits = ['dragon fruit', 'pear', 'apple', 'banana', 'grapes'];

Here we see that the .unshift() adds to the beginning of the array the new item I put into the method parameter. You can add as many new items as you want.

.concat() Example

let fruits = ['apple', 'banana', 'grapes'];
fruits.concat(['dragon fruit', 'pear']);
// fruits = ['apple', 'banana', 'grapes', 'dragon fruit', 'pear'];

Here we see that the .concat() takes an array as a parameter and adds the new items into the array.

The two methods did the exact same thing, so which one is better?

Both are perfectly valid. The only reason you MAY use one over the other is the number of entries you want to add to the array.

If there are multiple entries that I want to add I would use .concat().

If it’s just a single entry, then I would use .push().

However, you can accomplish the same goal using either.

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