Copy an Array with the Spread Operator

Use nested destructuring to access the value of an object within an object.

Nested Destructuring for Objects

Use the spread operator to copy a flat object. Note that this is a shallow copy.

Copy an Object with the Spread Operator

Use the spread operator to merge multiple arrays. This example uses two, but the same pattern can be used.

Merge Arrays using the Spread Operator

This is an example of how to use the flat method available on the array prototype in JavaScript.

Flatten a Nested Array in JavaScript with Array.prototype.flat

Using the spread operator you can merge objects. This example uses two objects, but the syntax is the same for more. Note that duplicate keys will be overridden.

Merge Objects with JavaScript's Spread Operator

Arrays can be iterated through using both for...in and for...of, but there are differences. This video shows that for...of accesses the values of each element and for...in accesses the indexes of each element.

For...in Loop vs. For...of Loop

Use the flatMap function to both map and flatten at the same time.

Array.prototype.flatMap from ES2019

Use these functions in order to flip back and forth between an Object and an Array.

Convert an Object to an Array and back again with Object.entries and Object.fromEntries

You can use optional chaining to access properties of an object. If the parent property exists, it acts as a typical dot accessor. If not, optional chaining prevents an error from being thrown and instead returns undefined.

Safely Access a Property on a JavaScript Object with Optional Chaining

You can use optional chaining to access elements in an array. If the array is null or undefined, attempting to access an element with optional chaining prevents an error from being thrown, returning undefined instead.

ES6 and Beyond

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