singleVariableDeclarations

Enforces one variable per declaration statement.

✅ This rule is included in the ts logical presets.

Declaring multiple variables in a single statement can reduce readability. Each variable declaration should be on its own line to make the code easier to read and maintain.

Examples

❌ Incorrect

let first, second, third;

const width = 100,
  height = 200;

for (let index = 0, length = 10; index < length; index++) {
  console.log(index);
}

✅ Correct

let first;
let second;
let third;

const width = 100;
const height = 200;

// Destructuring is allowed (single binding pattern)
const { first, second } = object;
const [width, height] = dimensions;

// For-of and for-in loops are fine
for (const item of items) {
  console.log(item);
}

Options

This rule is not configurable.

When Not To Use It

If you prefer to declare multiple variables in a single statement for brevity, you might choose to disable this rule.

Further Reading

• MDN documentation on variable declarations

Equivalents in Other Linters

• Biome: useSingleVarDeclarator
• Deno: single-var-declarator
• ESLint: one-var