noTemplateCurlyInString

Flags template literal placeholder syntax in regular strings.

• Category: Core
• Default: Not enabled (optional rule)

Behavior:

• Lint: reports template literal syntax (${expression}) found within regular (single or double quoted) strings
• This rule helps catch common mistakes where backticks should be used instead of quotes for template literals

Config:

rules: { noTemplateCurlyInString: 'warn' } // 'off' | 'warn' | 'error'

Example violations:

const name = "John"
const message = "Hello ${name}!" // Should use backticks: `Hello ${name}!`
const value = 42
const output = 'Value is ${value}' // Should use backticks: `Value is ${value}`

Correct usage:

const name = "John"
const message = `Hello ${name}!` // Correct template literal
const regularString = "This is just a string" // No template syntax
const escapedBrace = "This \\${is} escaped" // Escaped, won't be flagged

Examples

Violation:

function greet(name: string) {
  return "Hello ${name}!" // Error: should use template literal
}

Fix:

function greet(name: string) {
  return `Hello ${name}!` // Correct
}

Best practices

• Use template literals (backticks) when you need to interpolate variables
• Use regular strings when you have static content
• Keep this rule at warn during migration to avoid blocking builds
• Consider enabling this rule to catch copy-paste errors from template literals

Implementation details

This rule uses regex pattern matching to:

1. Find quoted strings (single or double quotes)
2. Check for ${...} patterns within those strings
3. Flag any matches as violations
4. Properly handle escaped braces that shouldn't be flagged