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crypto.randomFill() Method in Node.js
Both the crypto.randomFill() method and crypto.randomBytes() method are almost same. The only difference between the two is that – In randomFill() method the first argument is a buffer that will be filled. It also has a callback method that is called when an error is encountered only if the callback is configured.
Syntax
crypto.randomFill(buffer, [offset], [size], [callback])
Parameters
The above parameters are described as below −
buffer – This field contains the data content. Possible buffer types are: string, TypedArray, Buffer, ArrayBuffer, DataView. The size of the buffer cannot be greater than 2**31-1.
offset – The value of the offset from where randomFill will start. Default value is 0.
size – The size of the buffer after the offset. i.e. (buffer.length-offset). This value cannot be greater than 2**31-1.
callback – The function which will be called when an error is thrown.
Example
Create a file with name – randomFill.js and copy the below code snippet. After creating file, use the following command to run this code as shown in the example below −
node randomFill.js
randomFill.js
// Node.js program to demonstrate the flow of crypto.randomFill() method
// Importing the crypto module
const crypto = require('crypto');
const fs = require("fs");
// Initialising the buffer bytes value
const buf = Buffer.alloc(6);
// Calling the randomFill method with buffer and a callback
crypto.randomFill(buf, (err, buf) => {
if (err) throw err;
// Printing the buffer data value after filling
console.log(buf.toString('ascii'));
});
//Calling the randomFill with all the parameters defined above
crypto.randomFill(buf, 3, 2, (err, buf) => {
if (err) throw err;
// Printing the new random data in buffer
console.log(buf.toString('base64'));
});
// We can see that the output will be same for below function
crypto.randomFill(buf, 3, 3, (err, buf) => {
if (err) throw err;
console.log(buf.toString('base64'));
});Output
C:\home
ode>> node randomFill.js f!]"+– ZqHdoit8 ZqHdoit8
Example
Let's take a look at one more example.
// Node.js program to demonstrate the flow of crypto.randomFill() method
// Importing the crypto module
const crypto = require('crypto');
const fs = require("fs");
// Initialising the buffer bytes value using data view
const data = new DataView(new ArrayBuffer(16));
// Calling the randomFill method with buffer and a callback
crypto.randomFill(data, (err, buf) => {
if (err) throw err;
// Printing the randomFill data with encoding
console.log(Buffer.from(buf.buffer,
buf.byteOffset, buf.byteLength).toString('ascii'));
});Output
C:\home
ode>> node randomFill.js >h(Be#D8h0
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