unicorn/consistent-existence-index-check Style
What it does
Enforce consistent style for element existence checks with indexOf(), lastIndexOf(), findIndex(), and findLastIndex(). This rule ensures that comparisons for element presence are made with -1 rather than other comparison operators like < 0 or >= 0, improving clarity and consistency.
Why is this bad?
Using < 0 or >= 0 for element existence checks can lead to confusion, especially for developers who are not familiar with the specific behavior of these methods. The explicit === -1 or !== -1 makes the intent clearer and more readable, ensuring consistency across the codebase.
Examples
Examples of incorrect code for this rule:
javascript
const index = foo.indexOf("bar");
if (index < 0) {
}
const index = foo.indexOf("bar");
if (index >= 0) {
}Examples of correct code for this rule:
javascript
const index = foo.indexOf("bar");
if (index === -1) {
}
const index = foo.indexOf("bar");
if (index !== -1) {
}How to use
To enable this rule in the CLI or using the config file, you can use:
bash
oxlint --deny unicorn/consistent-existence-index-checkjson
{
"rules": {
"unicorn/consistent-existence-index-check": "error"
}
}