November 6, 2023
.filter(), and array destructuring.
Create a new array from an existing one
You can create a new array from an existing one by applying a function to each element of the array. The
.map() method is commonly used for this purpose.
Filter an array based on a condition
To filter an array based on a condition, use the
.filter() method. This method creates a new array with all elements that pass the test implemented by the provided function.
Combine map and filter
For more complex list comprehensions, you can chain
.filter() methods to first filter an array, then apply a function to the filtered results.
Use array destructuring for comprehension
.map() to perform more complex transformations.
Reduce an array to a single value
.reduce() method is used to apply a function against an accumulator and each element in the array to reduce it to a single value.
Comprehension with array spreading
The spread syntax
... allows an iterable such as an array to be expanded in places where zero or more arguments are expected. It can be used to concatenate arrays or to insert an array into another array.
Additional array methods
There are a couple other methods like
.flatMap() that are worth thinking about:
.some()checks if at least one element in the array passes the test implemented by the provided function.
.every()checks if all elements in the array pass the test implemented by the provided function.
.find()returns the value of the first element in the array that satisfies the provided testing function.
.flatMap()first maps each element using a mapping function, then flattens the result into a new array.
Custom iterator functions
For advanced array operations, consider creating custom iterator functions:
When dealing with large datasets or performance-critical applications, consider the efficiency of your array operations. Methods like
.filter() create new arrays, which could impact memory usage. Loop fusion, where you combine operations to minimize iterations over the data, can improve performance.
Using advanced patterns
Here's how you can use
.reduce() for array flattening:
Combine array methods with Promises and async/await for handling asynchronous operations elegantly:
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