JavaScript Array Methods Cheatsheet
## Iteration
```javascript
arr.forEach(fn) // Execute fn for each element
arr.map(fn) // Transform each element
arr.filter(fn) // Keep elements where fn returns true
arr.reduce(fn, init) // Reduce to single value
arr.find(fn) // First element matching fn
arr.findIndex(fn) // Index of first match
```
## Modification
```javascript
arr.push(el) // Add to end
arr.pop() // Remove from end
arr.unshift(el) // Add to beginning
arr.shift() // Remove from beginning
arr.splice(i, n, ...items) // Remove/insert at index
```
## Search & Test
```javascript
arr.includes(el) // Check if element exists
arr.indexOf(el) // Find index of element
arr.every(fn) // All elements pass test
arr.some(fn) // At least one passes test
```
## Transform
```javascript
arr.flat(depth) // Flatten nested arrays
arr.flatMap(fn) // Map then flatten
arr.slice(start, end) // Extract section
arr.concat(arr2) // Merge arrays
arr.sort(fn) // Sort in place
arr.reverse() // Reverse in place
```