Calculate two number in UTF-8 get NaN in Node.js

Question

I am using Socket in Node.js to get data and save them in buffer using utf8 format. And those data are number, I want to do some calculation but result in NaN.

var client = new net.Socket();
client.connect(PORT, HOST, function() {
    var commandstr = new Buffer("A5021E", "hex") 
    client.write(commandstr);
});

client.on('data', function(data) {
    var buff = new Buffer(data, 'utf8');
    ProcessBuffer(buff);
    client.destroy();
});

client.on('close', function() {
    console.log('Connection closed');
});

ProcessBuffer = function(recv_msg){
    var bp_s = recv_msg.toString('utf8').substring(65, 69); 

    console.log(parseInt(bp_s + 5)); //Do the calculation here and return in NaN
}

Answer 1

You need to convert the bp_s variable, which is a string, to a number before adding it to 5.

You can use the parseInt function [1]: parseInt(bp_s) .

So, your last line would be:

console.log(parseInt(bp_s) + 5);

Note that the parseInt function also allows you to define the radix of your number, as the second argument to the function. By default it is 10.

[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt