docs/src/rules/no-useless-concat.md
It's unnecessary to concatenate two strings together, such as:
const foo = "a" + "b";
This code is likely the result of refactoring where a variable was removed from the concatenation (such as "a" + b + "b"). In such a case, the concatenation isn't important and the code can be rewritten as:
const foo = "ab";
This rule aims to flag the concatenation of 2 literals when they could be combined into a single literal. Literals can be strings or template literals.
Examples of incorrect code for this rule:
::: incorrect
/*eslint no-useless-concat: "error"*/
const a = `some` + `string`;
// these are the same as "10"
const b = '1' + '0';
const c = '1' + `0`;
const d = `1` + '0';
const e = `1` + `0`;
:::
Examples of correct code for this rule:
::: correct
/*eslint no-useless-concat: "error"*/
// when a non string is included
const a = a + b;
const b = '1' + a;
const c = 1 + '1';
const d = 1 - 2;
// when the string concatenation is multiline
const e = "foo" +
"bar";
:::
This rule has no options.
If you don't want to be notified about unnecessary string concatenation, you can safely disable this rule.