JSON.parse未在JavaScript中创建json对象

Question

I am getting below string from upstream. Have no control over it.

b"{'text': 'Airtel Tower (@ BT Tower in Chasdmzoa, Delhi)', 'sentiment': '0.25'}"

I want to change the string to JSON. So the first thing I did was removing preceeding b'....' (upstream is a python program that produces utf-8 string as an output). So I am removing 'b' using substr..

str = msg.payload.substr(1);

Then I am trying to convert the string to JSON using JSON.stringify and JSON.parse .

console.log(typeof(str));
var t = JSON.stringify(str);
console.log(typeof(t));
var t = JSON.parse(t);
console.log("First:  " + t);
var t = JSON.parse(t);
console.log("Second  " + t);
x = t.text;
y = t["text"];
console.log(x + " ---- " + y);

Console Output:

string
string
First:  "{'text': 'Airtel Tower(@ KT Tower in Bang, Greater K
n), 'sentiment': '0.25'}"
Second  {'text': 'Vodafone Tower (@ LT Tower in Delhi, Greater K
), 'sentiment': '0.25'}
undefined ---- undefined

It fails to convert it to object even though JSON.stringify removed the extra quotes etc. and JSON.parse doesn't seem to work. What am I doing wrong?

Answer 1

There's an issue here: single-quoted string literals aren't valid JSON. JSON is based on JavaScript, but it's not the same thing. If you're writing an object literal inside JavaScript code, fine; if you actually need JSON, you need to use ".

Answer 2

 const input = "b'\\"{'text': 'Airtel Tower (@ BT Tower in Chasdmzoa, Delhi)', 'sentiment': '0.25'}\\"'"; const cleanString = str => str.split('"')[1].replace(/'/g, '"'); console.log(input); // Result console.log(JSON.parse(cleanString(input))); 

Explanation

1. Split the string with the double quote " as a delimiter
2. Get the second item. This will give you {'text': 'Airtel Tower (@ BT Tower in Chasdmzoa, Delhi)', 'sentiment': '0.25'}
3. Replace single quotes ' with double quotes " . This will give you {"text": "Airtel Tower (@ BT Tower in Chasdmzoa, Delhi)", "sentiment": "0.25"}
4. Call JSON.parse on the previous string to have your object

Answer 3

Simplest answer (for non-anti- eval -zealots):

var string = msg.payload.substring(3,msg.payload.length-2);
var t = eval("(" + string + ")");

If you can't stand, or can't use (strict mode?), eval , then you need to convert the single quotes to double quotes for parsing, as JSON only accepts double quotes:

var string = msg.payload.substring(3,msg.payload.length-2);
var t = JSON.parse(string.replace(/'/g, "\""));