noUnnecessaryTemplateExpression (JavaScript)

Language JavaScript (and super languages)

Summary

Rule available since: v2.4.13
Diagnostic Category: lint/nursery/noUnnecessaryTemplateExpression
This rule has a safe fix.
The default severity of this rule is information.
Sources:
- Inspired from @typescript-eslint/no-unnecessary-template-expression

How to configure

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{
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  "linter": {
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    "rules": {
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      "nursery": {
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        "noUnnecessaryTemplateExpression": "error"
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      }
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    }
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  }
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}

Description

Disallow unnecessary template expressions.

A template expression (or template literal) is unnecessary when it only contains string literal expressions that could be written as a regular string literal instead.

Examples

Invalid

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const a = `${'hello'}`;

code-block.js:1:11 lint/nursery/noUnnecessaryTemplateExpression  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This template expression is unnecessary.
  
  > 1 │ const a = `${'hello'}`;
      │           ^^^^^^^^^^^^
    2 │ 
  
  ℹ The template only contains string literal expressions. A regular string literal can be used instead.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.
  
  ℹ Safe fix: Replace the template expression with a string literal.
  
    1   │ - const·a·=·`${'hello'}`;
      1 │ + const·a·=·"hello";
    2 2 │

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const b = `${"world"}`;

code-block.js:1:11 lint/nursery/noUnnecessaryTemplateExpression  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This template expression is unnecessary.
  
  > 1 │ const b = `${"world"}`;
      │           ^^^^^^^^^^^^
    2 │ 
  
  ℹ The template only contains string literal expressions. A regular string literal can be used instead.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.
  
  ℹ Safe fix: Replace the template expression with a string literal.
  
    1 │ const·b·=·`${"world"}`;
      │           ---       --

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const c = `${'hello'}${'world'}`;

code-block.js:1:11 lint/nursery/noUnnecessaryTemplateExpression  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This template expression is unnecessary.
  
  > 1 │ const c = `${'hello'}${'world'}`;
      │           ^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ The template only contains string literal expressions. A regular string literal can be used instead.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.
  
  ℹ Safe fix: Replace the template expression with a string literal.
  
    1   │ - const·c·=·`${'hello'}${'world'}`;
      1 │ + const·c·=·"helloworld";
    2 2 │

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const d = `prefix_${'suffix'}`;

code-block.js:1:11 lint/nursery/noUnnecessaryTemplateExpression  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This template expression is unnecessary.
  
  > 1 │ const d = `prefix_${'suffix'}`;
      │           ^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ The template only contains string literal expressions. A regular string literal can be used instead.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.
  
  ℹ Safe fix: Replace the template expression with a string literal.
  
    1   │ - const·d·=·`prefix_${'suffix'}`;
      1 │ + const·d·=·"prefix_suffix";
    2 2 │

Valid

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// Template with a non-string-literal expression
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const a = `${someVariable}`;

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// Template with a non-string-literal interpolation mixed with text
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const b = `Hello, ${name}!`;

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// Tagged templates are never flagged
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const c = html`${'foo'}`;

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// Templates with newlines in the text part need the template syntax
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const d = `line one
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${'line two'}`;