Use the toLowerCase() method, which converts every character in the string to lowercase. For example:
let text = "HELLO";
let lowerText = text.toLowerCase(); // "hello"
How to convert string to upper and lowercase in JavaScript
Key takeaways:
The
toLowerCase()method converts all characters in a string to lowercase and returns a new string without altering the original. This is useful for case-insensitive comparisons or standardizing text.Similarly, the
toUpperCase()method transforms all characters to uppercase and is useful for emphasis or display purposes.JavaScript lacks a built-in capitalize method, but we can implement one by first converting the string to lowercase and then changing the first letter to uppercase. This method standardizes text with a capitalized first letter and lowercase for the rest.
Changing the case of strings is commonly needed in JavaScript for consistency, easier comparisons, and formatted display.
Working with strings is a common requirement in JavaScript, and sometimes we need to change the casing—either to uppercase or lowercase. Changing string cases helps with data consistency, easy comparisons, and enhanced display formatting. Let’s learn how we can easily perform these conversions, understand why they’re useful, and even try out some code examples.
Converting strings to lowercase
In JavaScript, we can use the toLowerCase() method to convert a string into a lowercase string. The toLowerCase() method will return a new string.
let str = "UPPER Case";let lowerCaseStr = str.toLowerCase();console.log(lowerCaseStr);
In the above code:
Line 1: We define a string variable
strwith the valueUPPER Case.Line 2: We use the
toLowerCase()method onstrto convert all characters to lowercase, storing the result inlowerCaseStr.Line 3: We log the lowercase version, which outputs
upper case.
Converting strings to uppercase
In JavaScript, we can also use the toUpperCase() method to convert a string into an uppercase string. The toUpperCase() method will return a new string.
var str = "uppercase";var upperCaseStr = str.toUpperCase();console.log(upperCaseStr);
In the above code:
Line 1: We define a string variable
strwith the valueuppercase.Line 2: We use the
toUpperCase()method onstrto convert all characters to uppercase, storing the result inupperCaseStr.Line 3: We log the lowercase version, which outputs
UPPERCASE.
Capitalize a string
We don’t have any in-build method to capitalize a string. However, we can implement our own method. The steps to capitalize a string are:
Convert the string to lowercase
Replace the first letter with an uppercase letter
function capitalize(str) {const lowerCaseString = str.toLowerCase(), // convert string to lowercasefirstLetter = str.charAt(0).toUpperCase(), // uppercase the first characterstrWithoutFirstChar = lowerCaseString.slice(1); // remove first character from lowercase stringreturn firstLetter + strWithoutFirstChar;}console.log(capitalize("javaScript"));console.log(capitalize("educative.io"));
In the above code:
Lines 1–7: We define the
capitalize()function to capitalize the string. Inside this function:Line 2: We convert the entire string to lowercase for consistency.
Line 3: We capitalize only the first character.
Line 4: We remove the first character from the lowercase string.
Line 6: We combine the capitalized first letter with the rest of the lowercase string, returning the result.
Lines 9–10: We call the
capatilize()function on two strings:javaScriptandeducative.io, and log the output. We can see theJavascriptandEducative.ioin the console.
Knowledge test
Let’s attempt a short quiz to assess your understanding.
1
Which method will you use to convert hello world to uppercase?
A)
toLowerCase()
B)
toUpperCase()
C)
toString()
Question 1 of 20 attempted
Conclusion
Converting string cases in JavaScript is simple but powerful for ensuring data consistency, enabling case-insensitive comparisons, and formatting content. By learning toUpperCase() and toLowerCase(), we can handle text with greater flexibility. Let’s keep practicing and exploring new ways to manage strings in JavaScript!
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