JavaScript toUpperCase(): Convert Text to Uppercase

The toUpperCase() method returns a new string with letters converted to uppercase while leaving the original string unchanged.

const text = "Welcome to Plus2net";
const upper = text.toUpperCase();
console.log(upper); // WELCOME TO PLUS2NET

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toUpperCase() syntax Top ↑

string.toUpperCase()

No argument is required.

Original string remains unchanged Top ↑

const original = "JavaScript";
const changed = original.toUpperCase();
console.log(original); // JavaScript
console.log(changed);  // JAVASCRIPT

Convert text interactively Top ↑

Result:

input.addEventListener('input', () => {
  result.textContent = input.value.toUpperCase();
});

See the related keyboard event tutorial.

Normalize text before a simple comparison Top ↑

const role = "ADMIN";
if (role.toUpperCase() === "ADMIN") {
  console.log("Matched");
}

Locale-sensitive uppercase Top ↑

const word = "istanbul";
console.log(word.toLocaleUpperCase("tr"));

Use toLocaleUpperCase() when language-specific casing matters.

Common mistakes Top ↑

Remember that this method returns a new string. It is a display/data-normalization tool, not a complete solution for locale-aware searching or authentication checks.

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Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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