Buffer.alloc(size[, fill[, encoding]])

版本历史

版本	变更
v10.0.0	尝试使用零长度缓冲区填充非零长度缓冲区，则会触发抛出异常。
v10.0.0	为 `fill` 指定无效字符串，则会触发抛出异常。
v8.9.3	为 `fill` 指定无效字符串，现在会导致缓冲区以零填充。
v5.10.0	新增于: v5.10.0

size <integer> 新的 Buffer 所需的长度。
fill <string> | <Buffer> | <Uint8Array> | <integer> 用于预填充新 Buffer 的值。 默认值: 0。
encoding <string> 如果 fill 是字符串，则这就是它的编码。 默认值: 'utf8'。

分配 size 个字节的新 Buffer。如果 fill 为 undefined，则 Buffer 将以零填充。

const buf = Buffer.alloc(5);

console.log(buf);
// 打印: <Buffer 00 00 00 00 00>

如果 size 大于 buffer.constants.MAX_LENGTH 或小于 0，则抛出 ERR_INVALID_OPT_VALUE。

如果指定了 fill，则分配的 Buffer 将通过调用 buf.fill(fill) 进行初始化。

const buf = Buffer.alloc(5, 'a');

console.log(buf);
// 打印: <Buffer 61 61 61 61 61>

如果同时指定了 fill 和 encoding，则分配的 Buffer 将通过调用 buf.fill(fill, encoding) 进行初始化。

const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');

console.log(buf);
// 打印: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>

调用 Buffer.alloc() 可能比替代的 Buffer.allocUnsafe() 慢得多，但可确保新创建的 Buffer 实例的内容永远不会包含来自先前分配的敏感数据，包括可能尚未分配给 Buffer 的数据。

如果 size 不是数值，则会抛出 TypeError。

History

Version	Changes
v10.0.0	Attempting to fill a non-zero length buffer with a zero length buffer triggers a thrown exception.
v10.0.0	Specifying an invalid string for `fill` triggers a thrown exception.
v8.9.3	Specifying an invalid string for `fill` now results in a zero-filled buffer.
v5.10.0	Added in: v5.10.0

size <integer> The desired length of the new Buffer.
fill <string> | <Buffer> | <Uint8Array> | <integer> A value to pre-fill the new Buffer with. Default: 0.
encoding <string> If fill is a string, this is its encoding. Default: 'utf8'.

Allocates a new Buffer of size bytes. If fill is undefined, the Buffer will be zero-filled.

const buf = Buffer.alloc(5);

console.log(buf);
// Prints: <Buffer 00 00 00 00 00>

If size is larger than buffer.constants.MAX_LENGTH or smaller than 0, ERR_INVALID_OPT_VALUE is thrown.

If fill is specified, the allocated Buffer will be initialized by calling buf.fill(fill).

const buf = Buffer.alloc(5, 'a');

console.log(buf);
// Prints: <Buffer 61 61 61 61 61>

If both fill and encoding are specified, the allocated Buffer will be initialized by calling buf.fill(fill, encoding).

const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');

console.log(buf);
// Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>

Calling Buffer.alloc() can be measurably slower than the alternative Buffer.allocUnsafe() but ensures that the newly created Buffer instance contents will never contain sensitive data from previous allocations, including data that might not have been allocated for Buffers.

A TypeError will be thrown if size is not a number.