JavaScript String isWellFormed() Method
Last Updated :
17 Jul, 2023
JavaScript String.isWellFormed() method is used to check if the string contains a lone surrogate or not. A lone surrogate is a string that contains Unicode characters in the range 0xD800–0xDBFF and 0xDC00–0xDFFF. It returns trues if the lone surrogate is not present. If the string is not well-formed it will give an error if we use the encodeURI() method on it.
Syntax:
isWellFormed()
Parameters: It does not take any parameter
Return Value: A boolean, true if no lone surrogate is present, and false if the lone surrogate is present.
Example 1: This example uses the isWellFormed() method on strings.
Javascript
const str1 = "ab\uD800" ;
const str2 = "new\uD800" ;
const str3 = "hello" ;
console.log(str1.isWellFormed());
console.log(str2.isWellFormed());
console.log(str3.isWellFormed());
|
Output:
false
false
true
Example 2: This example will perform the encodeURI function only on well-formed strings.
Javascript
const badFormed = "ab\uD800" ;
const wellFormed = "hello" ;
function checkFormation(str) {
if (str.isWellFormed()){
console.log(encodeURI(str))
}
}
checkFormation(wellFormed);
checkFormation(badFormed);
|
Output:
hello
Supported Browsers:
We have a complete list of Javascript string methods, to check those please go through this Javascript String reference article.
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