noForEach (since v12.1.0)
Prefer for...of statement instead of Array.forEach.
Here’s a summary of why forEach may be disallowed, and why for...of is preferred for almost any use-case of forEach:
Performance: Using
forEachcan lead to performance issues, especially when working with large arrays. When more requirements are added on,forEachtypically gets chained with other methods likefilterormap, causing multiple iterations over the same Array. Encouraging for loops discourages chaining and encourages single-iteration logic (e.g. using a continue instead offilter).Readability: While
forEachis a simple and concise way to iterate over an array, it can make the code less readable, especially when the callback function is complex. In contrast, using a for loop or afor...ofloop can make the code more explicit and easier to read.Debugging:
forEachcan make debugging more difficult, because it hides the iteration process.
Examples
Invalid
els.forEach(el => {
el
})nursery/noForEach.js:1:1 lint/nursery/noForEach ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
⚠ Prefer for...of instead of Array.forEach
> 1 │ els.forEach(el => {
│ ^^^^^^^^^^^^^^^^^^^
> 2 │ el
> 3 │ })
│ ^^
4 │
els['forEach'](el => {
el
})nursery/noForEach.js:1:1 lint/nursery/noForEach ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
⚠ Prefer for...of instead of Array.forEach
> 1 │ els['forEach'](el => {
│ ^^^^^^^^^^^^^^^^^^^^^^
> 2 │ el
> 3 │ })
│ ^^
4 │
Valid
for (const el of els) {
el
}