Buffer.byteLength(string[, encoding])
string
<string> | <Buffer> | <TypedArray> | <DataView> | <ArrayBuffer> | <SharedArrayBuffer> 用于计算长度的值。encoding
<string> 如果string
是字符串,则这就是它的编码。 默认值:'utf8'
。- 返回: <integer>
string
中包含的字节数。
使用 encoding
编码时返回字符串的字节长度。
这与 String.prototype.length
不同,String.prototype.length
不考虑用于将字符串转换为字节的编码。
对于 'base64'
、'base64url'
和 'hex'
,此函数假定输入有效。
对于包含非 base64/hex 编码数据(例如空格)的字符串,返回值可能大于从字符串创建的 Buffer
的长度。
const str = '\u00bd + \u00bc = \u00be';
console.log(`${str}: ${str.length} characters, ` +
`${Buffer.byteLength(str, 'utf8')} bytes`);
// 打印: ½ + ¼ = ¾: 9 characters, 12 bytes
当 string
为 Buffer
/DataView
/TypedArray
/ArrayBuffer
/SharedArrayBuffer
时,返回 .byteLength
报告的字节长度。
string
<string> | <Buffer> | <TypedArray> | <DataView> | <ArrayBuffer> | <SharedArrayBuffer> A value to calculate the length of.encoding
<string> Ifstring
is a string, this is its encoding. Default:'utf8'
.- Returns: <integer> The number of bytes contained within
string
.
Returns the byte length of a string when encoded using encoding
.
This is not the same as String.prototype.length
, which does not account
for the encoding that is used to convert the string into bytes.
For 'base64'
, 'base64url'
, and 'hex'
, this function assumes valid input.
For strings that contain non-base64/hex-encoded data (e.g. whitespace), the
return value might be greater than the length of a Buffer
created from the
string.
const str = '\u00bd + \u00bc = \u00be';
console.log(`${str}: ${str.length} characters, ` +
`${Buffer.byteLength(str, 'utf8')} bytes`);
// Prints: ½ + ¼ = ¾: 9 characters, 12 bytes
When string
is a Buffer
/DataView
/TypedArray
/ArrayBuffer
/
SharedArrayBuffer
, the byte length as reported by .byteLength
is returned.