unnecessaryConcatenation

Reports string concatenation using the + operator when both operands are string literals.

✅ This rule is included in the ts stylistic preset.

Concatenating string literals with the + operator is unnecessary and reduces code readability. String literals can be combined into a single literal, which is clearer and potentially more performant. This rule reports cases where two string literals are concatenated using the + operator when they could be combined into a single string literal.

Examples

❌ Incorrect

const message = "Hello" + "World";
const path = "directory" + "/" + "file.txt";
const multiLine =
  "This is a very long string that " + "continues on the next line";

✅ Correct

const message = "HelloWorld";
const path = "directory/file.txt";
const multiLine = "This is a very long string that continues on the next line";

// Concatenating with variables is allowed
const greeting = "Hello" + name;
const fullPath = basePath + "/file.txt";

// Template literals are a better choice for string interpolation
const template = `Hello ${name}`;

Options

This rule is not configurable.

When Not To Use It

If your codebase uses string concatenation intentionally for code clarity or consistency (for example, when breaking long strings across multiple lines for readability), you might choose to disable this rule. However, in most cases, combining string literals or using template literals improves code quality.

Further Reading

• MDN: String concatenation
• MDN: Template literals

Equivalents in Other Linters

• Biome: noUselessStringConcat
• ESLint: no-useless-concat
• Oxlint: eslint/no-useless-concat