Develop Reference

Why JSON.parse fails with this array-like string

I tried to JSON parse this
let string = `["\"test1, "\"test2"]`;
let array = JSON.parse(string);
console.log(array[0]);
It's fairly simple enough but I don't understand what's error message is supposed to tell
Uncaught SyntaxError: Unexpected token t in JSON at position 3

you are using template string to create a string.
it doesnt need a escape character for double quotes ".
type this:
let string = `["test1", "test2"]`;
let array = JSON.parse(string);
console.log(array[0])
you need a escape character for " only when you are using normal string. like this:
let string = "[\"test1\", \"test2\"]";
let array = JSON.parse(string);
console.log(array[0])
im not good at english.hope useful

How to parse an array inside a string into a javascript arrray

I have a string received from a database call as follows:
"[{'url':'https://www.example.com/','category':'popular'},{'url':'https://example2.com/','category':'new'}]"
I would like to parse the string into a typescript/JS array so that it is as follows:
[
{'url':'https://www.example.com/','category':'popular'},
{'url':'https://example2.com/','category':'new'}
]
How can I go about doing this? JSON.parse won't work as the string does not resemble a stringified JSON. Thanks!

Assuming there are no strings in it containing ', you can replace all occurrences of the single quote with double quotes, then you can parse it:
const str = "[{'url':'https://www.example.com/','category':'popular'},{'url':'https://example2.com/','category':'new'}]";
const arr = JSON.parse(str.replace(/'/g,'"'));
console.log(arr);

Replace single quotes with double quotes then JSON.parse
JSON.parse(
"[{'url':'https://www.example.com/','category':'popular'},{'url':'https://example2.com/','category':'new'}]"
.replace(/\'/g, '"')
)

Converting a string to array in javascript without eval()

I want to implement a counter for unique articles visited in my website, basically storing the ids of the articles the user has visited in a cookie. My issue is that the recovered value is, of course, a string. How would you convert a string that looks like this "['test','b','c']" to an array? Using eval is not advised, right?

Use JSON.parse to turn a string into an array:
const string = '["test","b","c"]';
const arr = JSON.parse(string);
console.log(arr[0]);
Note that you need to have proper JSON formatting, though - keys and non-numeric values need to have double quotes. Easiest to serialize automatically with JSON.stringify:
const arr = ["test","b","c"];
const str = JSON.stringify(arr);
console.log(str);
If you absolutely cannot change the single-quotes in the string you're working with originally, then use replace to turn it into something parseable:
const str = "['test','b','c']";
const jsonFormattedStr = str.replace(/'/g, '"');
const arr = JSON.parse(jsonFormattedStr);
console.log(arr[1]);

While using JSON.parse() is the correct way to convert data strings to usable objects, the string in your question is not valid JSON syntax. Namely the single quotes will result in an unexpected token error.
If your only issue is the quotes, then it becomes trivial to prepare your data for parsing:
var str = "['test','b','c']"
// convert to double quotes
str = str.split('\'').join('"')
// now parse
var arr = JSON.parse(str)
console.log(arr)

You need to convert the quotes to double quotes, and then use JSON.parse
let string = "['test','b','c']";
// replace quotes with double quotes
let stringFixed = string.replace(/'/g, '"');
// parse the string
let result = JSON.parse( stringFixed );

JavaScript json.parse string error

I want to parse this string to an array
var string= "['one','two']";
var result= JSON.parse(string);
It throws an error
`Unexpected token ' in JSON at position 1'
I believe my approach is right I just can't figure out why its throwing that error.

You should use double quotes:
var string = '["one", "two"]';
You can't use single quote in a JSON string.

Just make it like this
var string= '["one","two"]';
var result= JSON.parse(string);
Json standard requires that the string have double quotes inside.

Convert array formatted strings to object

I got
[[["汽車","car","Qìchē",""]],[["名詞",["汽車","車","轎車","車輛","車廂"],[["汽車",["car","automobile","auto"],,0.26497361],["車",["car","vehicle","lathe","machine","rook","turn"],,0.21967085],["轎車",["car","bus"],,0.020115795],["車輛",["vehicle","car"],,0.013611027],["車廂",["car"],,0.0042828997]]]],"en",,[["汽車",[4],0,0,1000,0,1,0]],[["car",4,[["汽車",1000,0,0],["車",0,0,0],["轎車",0,0,0],["車輛",0,0,0],["車廂",0,0,0]],[[0,3]],"car"]],,,[["en"]],27]
this from google translator
However I tried
JSON.parse(xhr.responseText);
It return an error Unexpected token

The problem is that this string contains multiple commas making your json invalid.
You could try to replace it for a single one before parsing
var x = '[[["汽車","car","Qìchē",""]],[["名詞",["汽車","車","轎車","車輛","車廂"],[["汽車",["car","automobile","auto"],,0.26497361],["車",["car","vehicle","lathe","machine","rook","turn"],,0.21967085],["轎車",["car","bus"],,0.020115795],["車輛",["vehicle","car"],,0.013611027],["車廂",["car"],,0.0042828997]]]],"en",,[["汽車",[4],0,0,1000,0,1,0]],[["car",4,[["汽車",1000,0,0],["車",0,0,0],["轎車",0,0,0],["車輛",0,0,0],["車廂",0,0,0]],[[0,3]],"car"]],,,[["en"]],27]'
.replace(/,{2,}/g, ",") // 2 or more replace for 1
JSON.parse(x);
Or if you have access to whatever is sending this string fix the output.

First you should remove an extra [] brackets by replacing that.
ex,
[["汽車","car","Qìchē",""]]
should be:
["汽車","car","Qìchē",""]
EDIT: you can refer to this answer: Parse Google Translate Json C#
You should try:
var str = '[[["汽車","car","Qìchē",""]],[["名詞",["汽車","車","轎車","車輛","車廂"],[["汽車",["car","automobile","auto"],,0.26497361],["車",["car","vehicle","lathe","machine","rook","turn"],,0.21967085],["轎車",["car","bus"],,0.020115795],["車輛",["vehicle","car"],,0.013611027],["車廂",["car"],,0.0042828997]]]],"en",,[["汽車",[4],0,0,1000,0,1,0]],[["car",4,[["汽車",1000,0,0],["車",0,0,0],["轎車",0,0,0],["車輛",0,0,0],["車廂",0,0,0]],[[0,3]],"car"]],,,[["en"]],27]';
var objstr = $.parseJSON(str);