valid-indexof-return.md

Disallow boolean cast of returning value of .indexOf() (valid-indexof-return)

The .indexOf() methods for both String and Array return numeric types. In some cases, it can be confused with the .includes() method and used as a boolean type.

Fail

if (arr.indexOf(x)) {}

arr.indexOf(x) ? foo : bar

arr.indexOf(x) && arr.map(item => item.id)

Pass

if (arr.indexOf(x) !== -1) {}

arr.includes(x) ? foo : bar

arr.indexOf(x) + offset