如何从node.js中的JSON将十六进制字符串解析为十六进制数字

Question

I want to save the addresses for an i2c device into a JSON file, but I have no idea how to parse the strings I get back into the addresses in hex notation.

const dev_address = this.parameters['DEVICE_ADDR']; // 0x04

First I tried .parseInt(this.parameters['DEVICE_ADDR'], 16) , then I thought the addresses might be some kind of byte[] and tried multiple things using buffer.from(str) and .toString('hex') without success.

How is this done?

---

Reference

'use strict';

const logger = require('../controller/LogController');
const i2c = require('i2c-bus');

class ArduinoPlug_on {
    constructor(parameters) {
      this.parameters = parameters;
    }

    run(env) {
      logger.debug('try connection', this.parameters);
      const dev_address = this.parameters['DEVICE_ADDR']; // 0x04
      const opt_address = this.parameters['OPTION_ADDR']; // 0x00

      const i2c1 = i2c.openSync(1);
      const bytesWritten = i2c1.i2cWriteSync(dev_address, 2, Buffer.from([opt_address,0x01]));
      if( bytesWritten == 0 ) {
        logger.error("could not write data", err);
      }
      i2c1.closeSync();
    }

    release(env) {
    }
}
module.exports = ArduinoPlug_on;

Answer 1

I think you're looking for something like this:

 // Convert a string with hex notation to number var somestring = "0xFF"; var n = parseInt(somestring); console.log(n); // 255 // Convert a number to string with hex notation var somenumber = 0xff; var s = somenumber.toString(16); console.log("0x" + s); // 0xff 

Answer 2

Converting from a String containing a hex number to decimal and back:

 let num = "0xff"; console.log(Number(num)); // to decimal console.log(`0x${Number(num).toString(16)}`); // to hex notation string