variableDeletions

Reports attempting to delete variables with the delete operator.

✅ This rule is included in the ts untyped preset.

The delete operator is only meant to remove properties from objects, not variables. Attempting to delete a variable in strict mode will cause a syntax error. In non-strict mode, it will silently fail and return false without actually deleting the variable, which can lead to confusing bugs.

Examples

❌ Incorrect

let count = 5;
delete count;

function calculate(value: number) {
  delete value;
}

✅ Correct

let count = 5;
count = undefined;

const obj = { property: 1 };
delete obj.property;

Options

This rule is not configurable.

When Not To Use It

If your codebase relies on non-standard behavior that involves deleting variables (which is highly discouraged), you might choose to disable this rule. For example, if you target a legacy runtime with non-standard JavaScript semantics, standard practices may not apply to you.

Further Reading

• MDN documentation on the delete operator
• MDN JavaScript Reference: Strict mode

Equivalents in Other Linters

• Deno: no-delete-var
• ESLint: no-delete-var
• Oxlint: eslint/no-delete-var