JavaScript string charCodeAt() vs codePointAt() All In One

JavaScript string charCodeAt() vs codePointAt() All In One

String.prototype.charCodeAt() vs String.prototype.codePointAt()

String 值的 charCodeAt() 方法返回 0 到 65535 之間的整數，表示給定索引處的 UTF-16 程式碼單元。

取值範圍： [0, 2^16]

2 ** 16
// 65536

2 ** 16 - 1
// 65535

'h'.charCodeAt()
//104
'h'.charCodeAt(0)
//104
'h'.charCodeAt(1)
// NaN

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/charCodeAt

String 值的 codePointAt() 方法返回一個非負整數，它是從給定索引開始的字元的 Unicode 程式碼點值。

'h'.codePointAt()
// 104
'h'.codePointAt(0)
// 'h'.codePointAt()
'h'.codePointAt(1)
// undefined

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/codePointAt

solutions

function scoreOfString(s: string): number {
  let sum: number = 0;
  for(let i = 0; i < s.length - 1; i++) {
    sum += Math.abs(s.charCodeAt(i) - s.charCodeAt(i+1));
  }
  return sum;
};

// function scoreOfString(s: string): number {
//   let sum: number = 0;
//   for(let i = 0; i < s.length - 1; i++) {
//     sum += Math.abs(s[i].charCodeAt(0) - s[i+1].charCodeAt(0));
//     // sum += arr[i] = Math.abs(s[i].codePointAt(0) - s[i + 1].codePointAt(0));
//   }
//   return sum;
// };

demos

function scoreOfString(s: string): number {
  let arr: number[] = new Array(s.length - 1).fill(0);
  for(let i = 0; i < s.length - 1; i++) {
    arr[i] = Math.abs(s[i].charCodeAt(0) - s[i+1].charCodeAt(0));
    // arr[i] = Math.abs(s[i].codePointAt(0) - s[i + 1].codePointAt(0));
  }
  return arr.reduce((sum, i) => sum += i, 0);
};

/* 
Line 5: Char 20: error TS2554: Expected 1 arguments, but got 0.


'h'.charCodeAt()
104
'h'.charCodeAt(0)
104
'h'.charCodeAt(1)
NaN

'h'.codePointAt()
104
'h'.codePointAt(0)
104
'h'.codePointAt(1)
undefined

 */

/* 

'h'.codePointAt()
104
'h'.charCodeAt()
104

 */

https://leetcode.com/problems/score-of-a-string/?envType=daily-question&envId=2024-06-01

function scoreOfString(s: string): number {
  const dict = {};
  // const begin = `a`.charCodeAt(0);
  // const end = `z`.charCodeAt(0);
  // for (let i = begin; i <= end; i++) {
  for (let i = 97; i <= 122; i++) {
    dict[String.fromCodePoint(i)] = i;
    // dict[String.fromCharCode(i)] = i;
  }
  // console.log(`dict =`, dict);
  let arr: number[] = new Array(s.length - 1).fill(0);
  for(let i = 0; i < s.length - 1; i++) {
    arr[i] = Math.abs(dict[s[i]] - dict[s[i + 1]]);
  }
  return arr.reduce((sum, i) => sum += i, 0);
};


/* 

const begin = `A`.charCodeAt();
const end = `z`.charCodeAt();
let dict = {};
for (let i = begin; i <= end; i++) {
  dict[String.fromCodePoint(i)] = i;
}
console.log(`dict =`, dict);
// {A: 65, ..., y: 121}

const begin = `A`.charCodeAt();
const end = `z`.charCodeAt();
let dict = {};
for (let i = begin; i <= end; i++) {
  dict[i] = String.fromCodePoint(i)
}
console.log(`dict =`, dict);
// {65: 'A', ..., 121: y}

 */

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String.fromCodePoint

convert number or string to ASCII

String.fromCodePoint(65);
//"A"
String.fromCodePoint(`65`);
//"A"

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/fromCodePoint

String.fromCharCode

String.fromCharCode(65)
// "A"
String.fromCharCode(`65`);
// "A"

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/fromCharCode

refs

convert number or string to ASCII in JavaScript All In One

https://www.cnblogs.com/xgqfrms/p/13333814.html

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