NodeJS: Data argument must be of type string/Buffer/TypedArray/DataView, how to fix?

12
votes

This Node JS code is from this project which I'm trying to understand.

// initialize the next block to be 1
let nextBlock = 1

// check to see if there is a next block already defined
if (fs.existsSync(configPath)) {
    // read file containing the next block to read
    nextBlock = fs.readFileSync(configPath, "utf8")
} else {
    // store the next block as 0
    fs.writeFileSync(configPath, parseInt(nextBlock, 10))
}

I get this error message:

Failed to evaluate transaction: TypeError [ERR_INVALID_ARG_TYPE]: The "data" argument must be of type string or an instance of Buffer, TypedArray, or DataView. Received type number (1)

I'm not too familiar with NodeJS, so could anyone explain to me how I can change this code to remove the error?

2
node.js

2 Answers

14
votes

So the error is saying the data (second argument of the fs.writeFileSync function) should be a string or a buffer...etc but instead got a number.

To resolve, convert the second argument to string as shown: 

fs.writeFileSync(configPath, parseInt(nextBlock, 10).toString())
3
votes

If data is JSON:

Write to file:

let file_path = "./downloads/";
let file_name = "mydata.json";


let data = {
    title: "title 1",
};
fs.writeFileSync(file_path + file_name, JSON.stringify(data));

Read from file:

let data = fs.readFileSync(file_path + file_name);
data = JSON.parse(data);
console.log(data);