String.prototype.charCodeAt()

Baseline

20157

charCodeAt() UTF-16 0 65535

charCodeAt() UTF-16 String.prototype.codePointAt()

const sentence = "The quick brown fox jumps over the lazy dog.";

const index = 4;

console.log(
  `Character code ${sentence.charCodeAt(index)} is equal to ${sentence.charAt(
    index,
  )}`,
);
// : "Character code 113 is equal to q"

charCodeAt(index)

index: 0 undefined 0

0 65535 index UTF-16 index 0 str.length - 1 charCodeAt() NaN

0 str str.length - 1

Unicode 0 1114111 (0x10FFFF) charCodeAt() 65536 16 65535 charCodeAt(i) charCodeAt(i + 1) 2 codePointAt(i) Unicode UTF-16 Unicode

charCodeAt()

Unicode A 65

"ABC".charCodeAt(0); // returns 65

charCodeAt() Unicode

const str = "";
console.log(str.charCodeAt(0)); // 55362 d842 Unicode 
console.log(str.charCodeAt(1)); // 57271 dfb7 Unicode

Unicode String.prototype.codePointAt()

const str = "";
console.log(str.codePointAt(0)); // 134071

: charCodeAt() codePointAt() API codePointAt()

Unicode FAQ UTF-16 Unicode

// constants
const LEAD_OFFSET = 0xd800 - (0x10000 >> 10);
const SURROGATE_OFFSET = 0x10000 - (0xd800 << 10) - 0xdc00;

function utf16ToUnicode(lead, trail) {
  return (lead << 10) + trail + SURROGATE_OFFSET;
}
function unicodeToUTF16(codePoint) {
  const lead = LEAD_OFFSET + (codePoint >> 10);
  const trail = 0xdc00 + (codePoint & 0x3ff);
  return [lead, trail];
}

const str = "";
console.log(utf16ToUnicode(str.charCodeAt(0), str.charCodeAt(1))); // 134071
console.log(str.codePointAt(0)); // 134071


ECMAScript 2027 LanguageSpecification # sec-string.prototype.charcodeat

MDN

MDN 2025925

GitHub