js String charCodeAt All In One

The charCodeAt() method returns an integer between 0 and 65535 representing the UTF-16 code unit at the given index.

charCodeAt() 方法返回一个介于 0 和 65535 之间的整数，表示给定索引处的 UTF-16 代码单元。

单个字符，默认索引是 0;
如果索引超出范围， 返回值 NaN;

// 默认 index 是 0 ✅
`a`.charCodeAt()
// 97

`a`.charCodeAt(0)
// 97

// 索引超出范围， 返回值 NaN; ❌
`a`.charCodeAt(1)
// NaN

多个字符，按照指定的索引返回

const str = `abc`
// 'abc'

str.charCodeAt()
// 97

str.charCodeAt(0)
// 97
str.charCodeAt(1)
// 98
str.charCodeAt(2)
// 99

Unicode & ASCII

Unicode code points range from 0 to 1114111 (0x10FFFF).
The first 128 Unicode code points are a direct match of the ASCII character encoding.

charAt

The String object's charAt() method returns a new string consisting of the single UTF-16 code unit located at the specified offset into the string.

String 对象的 charAt() 方法返回一个新字符串，该字符串由位于字符串中指定偏移量的单个 UTF-16 代码单元组成。

const str = 'abc';

console.log(str.charAt());
console.log(str.charAt(0));
console.log(str.charAt(1));
console.log(str.charAt(2));
console.log(str.charAt(3));

// "a"
// "a"
// "b"
// "c"
// ""

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

refs

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

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来源： https://www.cnblogs.com/xgqfrms/p/16559141.html