JavaScript Tutorials

JavaScript String toWellFormed()
Syntax & Examples

String.toWellFormed() method

The toWellFormed() method of the String class in JavaScript returns a string where all lone surrogates of the original string are replaced with the Unicode replacement character U+FFFD.

Syntax of String.toWellFormed()

The syntax of String.toWellFormed() method is:

toWellFormed()

This toWellFormed() method of String returns a string where all lone surrogates of this string are replaced with the Unicode replacement character U+FFFD.

Return Type

String.toWellFormed() returns value of type String.


✐ Examples

1 Using toWellFormed() method to replace lone surrogates

In JavaScript, the toWellFormed() method replaces lone surrogates with the Unicode replacement character U+FFFD.

For example,

  1. We define a string variable str containing a lone surrogate '\uD800'.
  2. We use the toWellFormed() method to replace the lone surrogate with U+FFFD.
  3. The result is stored in the variable wellFormedStr.
  4. We log wellFormedStr to the console using the console.log() method.

JavaScript Program

const str = '\uD800';
const wellFormedStr = str.toWellFormed();
console.log(wellFormedStr);

Output

�

2 Using toWellFormed() method on a string with multiple lone surrogates

In JavaScript, the toWellFormed() method can replace multiple lone surrogates in a string.

For example,

  1. We define a string variable str containing multiple lone surrogates '\uD800\uDC00\uD800'.
  2. We use the toWellFormed() method to replace the lone surrogates with U+FFFD.
  3. The result is stored in the variable wellFormedStr.
  4. We log wellFormedStr to the console using the console.log() method.

JavaScript Program

const str = '\uD800\uDC00\uD800';
const wellFormedStr = str.toWellFormed();
console.log(wellFormedStr);

Output

���

3 Using toWellFormed() method on a well-formed string

In JavaScript, the toWellFormed() method does not alter a string that is already well-formed.

For example,

  1. We define a string variable str containing a well-formed Unicode string 'Hello \uD83D\uDE00'.
  2. We use the toWellFormed() method.
  3. The result is stored in the variable wellFormedStr.
  4. We log wellFormedStr to the console using the console.log() method.

JavaScript Program

const str = 'Hello \uD83D\uDE00';
const wellFormedStr = str.toWellFormed();
console.log(wellFormedStr);

Output

Hello 😀

Summary

In this JavaScript tutorial, we learned about toWellFormed() method of String: the syntax and few working examples with output and detailed explanation for each example.