How to use the codePointAt method in JavaScript

by Janeth Kent Date: 23-07-2021 javascript


The JavaScript codePointAt method has more or less the same function as the charCodeAt method, used to get the 16-bit Unicode representation of the character at a certain position in a string.

However, certain characters present a small problem, as they use two 16-bit units, so the charCodeAt method will only return half of the representation of these special characters.

The codePointAt method was introduced in JavaScript in its ES2015 version in order to get Unicode representations of characters that use two 16-bit units instead of just one. In general, you can get all Latin or Saxon characters using the charCodeAt method, but not Chinese or Japanese characters. The codePointAt method accepts as a parameter the index of the string to which the method is applied, which may be a standard string declared with single or double quotes, a String object or a template literal

The value returned by the codePointAt method will be undefined when the index we pass to the method has no representation.

For example, to get the Unicode representation in decimal or hexadecimal formed by two Unicode UTF-16 units of the character Unicode UTF-16 we would have to use the charCodeAt method twice:

 
// Decimal representation  
const firstPart = 'Unicode UTF-16'.charCodeAt(0); // 55362  
const secondPart= 'Unicode UTF-16'.charCodeAt(1); // 57271    
// Hexadecimal representation  
const firstPart = 'Unicode UTF-16'.charCodeAt(0).toString(16); // d842  
const secondPart = 'Unicode UTF-16'.charCodeAt(1).toString(16); // dfb7
 

You can see that if you put both parts together and show them through the console, you get the character Unicode UTF-16:

 
console.log('ud842udfb7'); // Unicode UTF-16
 

However, it is possible to obtain the character representation using the codePointAt method only once:

 
// Decimal representation  
const decimal = 'Unicode UTF-16'.codePointAt>(0); // 134071    
// Hexadecimal representation  
const hexadecimal = 'Unicode UTF-16'.codePointAt(0).toString(16); // 20bb7
 

To check that the result is correct, simply display the result via the console:

 
console.log('u{20bb7}');
 

If you use a String object, the process is exactly the same:

 
const mychain = new String('Unicode UTF-16'); 
    
// Decimal representation  
const decimal = mychain.codePointAt(0); // 134071 
   
// Hexadecimal representation  
const hexadecimal = mychain.codePointAt(0).toString(16); // 20bb7

 
by Janeth Kent Date: 23-07-2021 javascript hits : 6989  
 
Janeth Kent

Janeth Kent

Licenciada en Bellas Artes y programadora por pasión. Cuando tengo un rato retoco fotos, edito vídeos y diseño cosas. El resto del tiempo escribo en MA-NO WEB DESIGN END DEVELOPMENT.

 
 
 

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