How to convert a string to uppercase in JavaScript
Łukasz Holeczek
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Converting strings to uppercase is essential for data normalization, case-insensitive comparisons, creating display headers, and implementing features like search matching or consistent text formatting in JavaScript applications.
With over 25 years of experience in software development and as the creator of CoreUI, I’ve implemented uppercase conversion extensively in components like form labels, button text, navigation headers, and search functionality where consistent capitalization enhances user experience and data processing.
From my extensive expertise, the most straightforward and universally supported solution is using the built-in toUpperCase() method.
This approach is simple, efficient, and specifically designed for case conversion with excellent browser compatibility.
Use the toUpperCase() method to convert all characters in a string to uppercase.
const text = 'hello world'
const uppercase = text.toUpperCase()
// Result: 'HELLO WORLD'
The toUpperCase() method converts all alphabetic characters in the string to their uppercase equivalents and returns a new string without modifying the original. In this example, 'hello world'.toUpperCase() transforms all lowercase letters to uppercase, resulting in ‘HELLO WORLD’. Non-alphabetic characters like numbers, spaces, and punctuation remain unchanged. The method handles international characters correctly, converting accented letters and other Unicode characters to their proper uppercase forms.
Best Practice Note:
This is the same approach we use in CoreUI components for creating consistent header text, button labels, and implementing case-insensitive search functionality across our component library.
For locale-specific uppercase conversion, use toLocaleUpperCase() which respects language-specific rules. This method is universally supported across all browsers and JavaScript environments. When comparing strings case-insensitively, convert both strings to the same case before comparison.
