90 lines
2.7 KiB
Markdown
90 lines
2.7 KiB
Markdown
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---
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title: Nodejs- Buffer
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---
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## Buffer
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Binary is simply a set or a collection of `1` and `0`. Each number in a binary, each 1 and 0 in a set are called a _bit_. Computer converts the data to this binary format to store and perform operations. For example, the following are five different binaries:
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`10, 01, 001, 1110, 00101011`
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JavaScript does not have a byte type data in its core API. To handle binary data Node.js includes a binary buffer implementation with a global module called `Buffer`.
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### Creating a Buffer
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There are different ways you can create a buffer in Node.js. You can create an empty buffer by with a size of 10 bytes.
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```javascript
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const buf1 = Buffer.alloc(10);
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```
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From UTF-8-encoded strings, the creation is like this:
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```javascript
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const buf2 = Buffer.from('Hello World!');
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```
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There are different accepted encoding when creating a Buffer:
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* ascii
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* utf-8
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* base64:
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* latin1
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* binary
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* hex
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There are three separate functions allocated in the Buffer API to use and create new buffers. In above examples we have seen `alloc()` and `from()`. The third one is `allocUnsafe()`.
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```javascript
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const buf3 = Buffer.allocUnsafe(10);
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```
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When returned, this function might contain old data that needs to be overwritten.
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### Interactions with Buffer
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There are different interactions that can be made with the Buffer API. We are going to cover most of them here. Let us start with converting a buffer to JSON.
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```javascript
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let bufferOne = Buffer.from('This is a buffer example.');
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console.log(bufferOne);
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// Output: <Buffer 54 68 69 73 20 69 73 20 61 20 62 75 66 66 65 72 20 65 78 61 6d 70 6c 65 2e>
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let json = JSON.stringify(bufferOne);
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console.log(json);
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// Output: {"type": "Buffer", "data": [84,104,105,115,32,105,115,32,97,32,98,117,102,102,101,114,32,101,120,97,109,112,108,101,46]}
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```
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The JSON specifies that the type of object being transformed is a Buffer, and its data. Converting an empty buffer to JSON will show us that it contains nothing but zeros.
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```javascript
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const emptyBuf = Buffer.alloc(10);
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emptyBuf.toJSON();
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// Output: { "type": "Buffer", "data": [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ] }
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```
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Do notice that, Buffer API also provides a direct function `toJSON()` to convert a buffer into a JSON object. To examine the size of a buffer, we can use `length` method.
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```javascript
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emptyBuf.length;
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// Output: 10
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```
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Now let us convert buffer to a readable string, in our case, the utf-8 encoded.
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```javascript
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console.log(bufferOne.toString('utf8'));
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// Output: This is a buffer example.
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```
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`.toString()` by default converts a buffer to a utf-8 format string. This is how you decode a buffer. If you specify an encoding you can convert the buffer to another encoding
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```javascript
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console.log(bufferOne.toString('base64'));
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```
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