Node.js Buffer.writeBigUInt64LE() Method

Last Updated : 7 Jul, 2020
The Buffer.writeBigUInt64LE() method is an inbuilt application programming interface of class Buffer within the Buffer module which is used to writes little endian 64-bits Big integer value to an allocated buffer at the specified offset. Syntax: 
Buffer.writeBigUInt64LE( value, offset )
Parameters:
  • value: This parameter specifies big integer value to be written to the buffer. It should be a valid 64 bits little endian Big integer value. Behavior is undefined when value is anything other than this.
  • offset: It specifies the number of bytes to skip before write or simply signify the index in the buffer. The value of offset lies 0 <= offset <= Buffer.length - 8. Its default value is 0.
    • Return Value: This method returns an unsigned integer value that is the sum of offset and number of bytes written. Below examples illustrate the use of Buffer.writeBigUInt64LE() method in Node.js: Example 1: Filename: index.js javascript 
    // Node.js program to demonstrate the
// buffer.writeBigUInt64LE() method 
const buf = Buffer.allocUnsafe(8);

// Writing big integer value into buffer
// by using writeBigUInt64LE() method
buf.writeBigUInt64LE(0x01030405060708n, 0);

// display the buffer
console.log(buf);
    Run the index.js file using the following command: 
    node index.js
    Output: 
    <Buffer 08 07 06 05 04 03 01 00>
    Example 2: Filename: index.js javascript 
    // Node.js program to demonstrate the
// buffer.writeBigUInt64LE() method 
const buf = Buffer.allocUnsafe(8);

// writing big integer value into buffer
// by using writeBigUInt64LE() method
buf.writeBigUInt64LE(0xaa03040506efffn, 0);

// Display the buffer
console.log(buf);
    Run the index.js file using the following command: 
    node index.js
    Output: 
    <Buffer ff ef 06 05 04 03 aa 00>
    Reference:https://nodejs.org/dist/latest-v12.x/docs/api/buffer.html#buffer_buf_writebiguint64le_value_offset
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