Lodash _.toUpper() Method

Beginner
5 min read
Updated: Nov 2026
5 examples
String
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Definition

Converts a string, as a whole, to uppercase — same idea as String#toUpperCase. Separators stay put; only letters change case. Part of Lodash String (stable since 4.0.0 — not deprecated).

Pass the string and options shown below. Check the return type before you chain another helper.

Syntax

Call _.toUpper. Start with this line.

Lodash
_.toUpper([string=''])
CallWhat it does
_.toUpper([string=''])Primary signature.
_.toUpper(string)Transform or inspect a string.

Prefer import toUpper from "lodash/toUpper" when you want a smaller bundle.

Library declarations
Lodash
_.toUpper([string=''])

Parameters

ParameterDescription
stringOptional. Value to convert (default ''; non-strings are coerced)

Return Value

Return ValueDescription
*New uppercased string

Lodash Examples

Example 1 — Official: Hyphenated String

Uppercase letters; keep the dashes.

Lodash
console.log(_.toUpper("--foo-bar--"));
// '--FOO-BAR--'
Try It Yourself

How It Works

  1. Input. Lowercase text with hyphens.
  2. Convert. Each letter becomes uppercase.
  3. Keep. - characters stay in place.
  4. Docs. Matches the official first example.

Example 2 — Official: camelCase Collapses Visually

Case goes away — word boundaries from capitals disappear.

Lodash
console.log(_.toUpper("fooBar"));
// 'FOOBAR'
Try It Yourself

How It Works

  1. Input. fooBar uses a capital for the second word.
  2. Upper. Every letter becomes uppercase.
  3. Result. One flat word: FOOBAR.
  4. Tip. Prefer _.upperCase if you need spaced words.

Example 3 — Official: Underscored Text

Underscores stay; letters rise to uppercase.

Lodash
console.log(_.toUpper("__foo_bar__"));
// '__FOO_BAR__'
Try It Yourself

How It Works

  1. Input. Lowercase identifier-style string.
  2. Convert. foo / bar become uppercase.
  3. Keep. Underscores are unchanged.
  4. Docs. Matches the official third example.

Example 4 — Format a Display Label

Normalize mixed input before showing a badge or code.

Lodash
var status = "active";

console.log("STATUS: " + _.toUpper(status));
// 'STATUS: ACTIVE'
Try It Yourself

How It Works

  1. Input. A lowercase status value.
  2. Upper. _.toUpper makes it display-ready.
  3. Use. Common for labels, SKUs, and short codes.
  4. Note. For title-style text, try _.startCase.

Example 5 — Pair with _.toLower

Same input, opposite case helpers.

Lodash
var s = "Foo-Bar";

console.log(_.toUpper(s)); // 'FOO-BAR'
console.log(_.toLower(s)); // 'foo-bar'
Try It Yourself

How It Works

  1. toUpper. All letters become uppercase.
  2. toLower. All letters become lowercase.
  3. Shared. Both keep the hyphen.
  4. Next. See the _.toLower tutorial.
Compatibility

Browser & Runtime Support

_.toUpper is a Lodash String helper available since 4.0.0. It runs anywhere Lodash runs — modern browsers (via CDN or bundle) and Node.js / Bun / Deno with npm install lodash.

✓ Stable · Lodash 4.x

_.toUpper()

Available in [email protected] full builds and the lodash/toUpper modular import. Works in evergreen browsers and current Node LTS when Lodash is installed.

100% With Lodash 4.x
Google Chrome Supported · Desktop & Mobile
Full support
Mozilla Firefox Supported · Desktop & Mobile
Full support
Apple Safari Supported · macOS & iOS
Full support
Microsoft Edge Supported · Chromium
Full support
Internet Explorer No native support · Use a polyfill
Polyfill
Opera Supported · Modern versions
Full support
Samsung Internet Supported · Android
Full support
Bun Supported · JavaScript runtime
Supported
Deno Supported · JavaScript runtime
Supported
Node.js Supported · Server runtime
Supported
Android WebView Supported · Modern WebView
Full support
_.toUpper Since 4.0.0

Bottom line: Safe for production once Lodash is on the page. Prefer import toUpper from "lodash/toUpper" for smaller builds. Native String#toUpperCase is fine when you do not need Lodash.

Frequently Asked Questions

_.toUpper([string='']) converts the whole string to uppercase, like String#toUpperCase. Official: _.toUpper('--foo-bar--') → '--FOO-BAR--'.
_.toUpper only changes letter case and keeps separators. _.upperCase splits into space-separated uppercase words (e.g. '--foo-bar--' → 'FOO BAR').
For plain strings they usually match. Lodash coerces non-strings first and fits the rest of the Lodash string API.
No. Strings are immutable. _.toUpper always returns a new string.
Use _.toLower for lowercase normalization, slugs, or case-insensitive storage. Use _.toUpper for labels, codes, and display caps.
Use import toUpper from "lodash/toUpper" or require("lodash/toUpper"). Full build: import _ from "lodash" then _.toUpper.

Next: _.trim()

Remove leading and trailing characters from a string.

_.trim() tutorial →

About the author

Mari Selvan M P
Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

  • Experience 12 years building web and cloud systems
  • Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

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