JavaScript objects can only store character sequence values and can not store binary data. But you may need to read and store binary data when making I/O operations such as read/write image file, read/write binary stream through a network, etc. To resolve this issue, Node JS provides the Buffer module to store and manipulate binary data. This is a built-in module, you can use it directly without requiring any modules.
1. Buffer And Character Encoding.
The Buffer instance is typically used to represent the sequence of encoded characters, such as utf-8, ucs2, base64, or hexadecimal encoded data. By using explicit character encoding, you can switch between the Buffer instance and the normal JavaScript string.
console.log("string1 is a english string totally.")
var string1 = "hello dev2qa.com";
var buffer1 = Buffer.from(string1, 'ascii');
console.log("buffer1 = " + buffer1);
console.log("buffer1 to ascii = " + buffer1.toString('ascii'));
console.log("buffer1 to utf-8 = " + buffer1.toString('utf-8'));
console.log("buffer1 to base64 = " + buffer1.toString('base64'));
console.log("string2 contains chinese character, so need to use utf-8 encoding to create the Buffer object.")
var string2 = "你好 dev2qa.com";
var buffer2 = Buffer.from(string2, 'utf-8');
console.log("buffer2 = " + buffer2);
console.log("buffer2 to ascii = " + buffer2.toString('ascii'));
console.log("buffer2 to utf-8 = " + buffer2.toString('utf-8'));
console.log("buffer2 to base64 = " + buffer2.toString('base64'));
Below is the output when executing the above code.
string1 is a english string totally. buffer1 = hello dev2qa.com buffer1 to ascii = hello dev2qa.com buffer1 to utf-8 = hello dev2qa.com buffer1 to base64 = aGVsbG8gZGV2MnFhLmNvbQ== string2 contains chinese character. buffer2 = 你好 dev2qa.com buffer2 to ascii = d= e%= dev2qa.com buffer2 to utf-8 = 你好 dev2qa.com buffer2 to base64 = 5L2g5aW9IGRldjJxYS5jb20=
2. Create Buffer Object.
The below code shows an example of how to create a Buffer object in Node JS.
// Create a Buffer object with size 10, filled with 0.
var buffer1 = Buffer.alloc(10);
console.log("buffer1 = " + buffer1.toString("utf8"));
console.log("buffer1 length = " + buffer1.length);
// Create a Buffer object with size 100, filled with 0x1.
var buffer2 = Buffer.alloc(100, 1);
console.log("buffer2 = " + buffer1.toString("hex"));
console.log("buffer2 length = " + buffer2.length);
/* Create a uninitialized Buffer object with size 10. This method is faster than Buffer.alloc()，But the return Buffer may contain old data，So need to use fill() or write() method to overwrite. */
var buffer3 = Buffer.allocUnsafe(10);
console.log("buffer3 = " + buffer1.toString("utf-8"));
console.log("buffer3 length = " + buffer3.length);
// Create a Buffer object contains [0x1, 0x2, 0x3].
var buffer4 = Buffer.from([1, 2, 3]);
console.log("buffer4 = " + buffer4.toString());
console.log("buffer4 length = " + buffer4.length);
// Create a Buffer object contains UTF-8 encoding character [0x74, 0xc3, 0xa9, 0x73, 0x74].
var buffer5 = Buffer.from('tést');
console.log("buffer5 = " + buffer5.toString());
console.log("buffer5 length = " + buffer5.length);
// Create a Buffer object contains Latin-1 encoding character [0x74, 0xe9, 0x73, 0x74].
var buffer6 = Buffer.from('tést', 'latin1');
console.log("buffer6 = " + buffer6);
console.log("buffer6 length = " + buffer6.length);
Below is the output of the above code.
buffer1 length = 10 buffer2 = 00000000000000000000 buffer2 length = 100 buffer3 = buffer3 length = 10 buffer4 = buffer4 length = 3 buffer5 = tést buffer5 length = 5 buffer6 = t�st buffer6 length = 4
3. Write / Read Data To / From Buffer.
// Create a buffer, allocate 25 character space.
var buffer = Buffer.alloc(25);
// Write a string to the buffer and return the buffer length.
var length = buffer.write("http://www.dev2qa.com");
// Output the buffer.
console.log("buffer : " + buffer);
// Output the buffer character length.
console.log("buffer length : " + length);
// Read the first 10 character of the buffer.
console.log("buffer first 10 character : " + buffer.toString('utf8', 0, 10));
Below is the output of the above code.
buffer : http://www.dev2qa.com buffer length : 21 buffer first 10 character : http://www
4. Buffer To JSON.
var buffer = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]); console.log(buffer.toJSON());
Below is the output.
{ type: 'Buffer', data: [ 1, 2, 3, 4, 5 ] }
5. Concat Buffer.
// Create the first buffer.
var buffer1 = Buffer.from(('dev2qa.com'));
// Create the second buffer.
var buffer2 = Buffer.from((' is a very good website.'));
// Concat two buffer to a new one.
var buffer3 = Buffer.concat([buffer1,buffer2]);
// Print out the new buffer.
console.log("buffer3 : " + buffer3.toString());
Below is the output.
buffer3 : dev2qa.com is a very good website.
6. Compare Buffer.
// Create the first buffer with a number string.
var buffer1 = Buffer.from('100');
// Create the second buffer with a character string.
var buffer2 = Buffer.from('www.dev2qa.com');
// Compare two buffer value. The result is a number.
var result = buffer1.compare(buffer2);
var message = "";
if(result < 0) {
message = "buffer1 is smaller than buffer2";
}else if(result == 0){
message = "buffer1 is equal to buffer2";
}else {
message = "buffer1 is bigger than buffer2.";
}
console.log(message);
Below is the output of the above code.
buffer1 is smaller than buffer2
7. Copy Buffer.
var buffer1 = Buffer.from('hello www.dev2qa.com ');
var buffer2 = Buffer.from('http://');
// Copy buffer2's value to the specified position in buffer1.
buffer2.copy(buffer1, 6);
console.log(buffer1.toString());
Below is the output.
hello http://www.dev2qa.com
8. Slice Buffer.
var buffer1 = Buffer.from('http://www.dev2qa.com');
// Slice buffer1 and return buffer2.
var buffer2 = buffer1.slice(7, buffer1.length);
console.log("buffer2 : " + buffer2.toString());
Below is the output.
buffer2 : www.dev2qa.com