How to convert an input of type string into type object array in node js

Question

I am creating a cli app & I get an input from the user : print [{name:'joe', age:19}] where arg = [{name:'joe', age:19}]

But when I do typeof arg, it returns string. I tried using json.parse [throws error], slice(1,-1) [removes outer array brackets & type remains string] and Array.from(arg) [splits all the brackets & letters into different elements].

So how do I convert [{name:'joe', age:19}] into type object array?

Code Snippet :

vorpal
.command('input <array>')
.action(function(args,cb) {
  let array = args.array;
  this.log(array); //returns [{name:'joe',age:19}]
  this.log(typeof array);  //returns string
  cb();

});

Does this post answer your question? https://stackoverflow.com/questions/4351521/how-do-i-pass-command-line-arguments-to-a-node-js-program — Sjoerd, Nov 14 '18 at 09:42
@Sjoerd that should not be a problem because I am using a library called vorpal js to accept arguments but it always returns the argument as a string. — Endemic, Nov 14 '18 at 09:46
@YongQuan I get : SyntaxError: Unexpected token n in JSON at position 2 — Endemic, Nov 14 '18 at 09:51
@YongQuan in JSON, object keys and strings must be wrapped in double quotes `"` — Kaddath, Nov 14 '18 at 09:53
Can your users use proper JSON format , for example: [{"name":"joe", "age":19}] ? — Grzesiek Danowski, Nov 14 '18 at 09:55
@GrzesiekDanowski Its possible but I guess then I am forcing the user to follow a particular syntax (in this case JSON). — Endemic, Nov 14 '18 at 09:59
@Endemic you are creator of the cli and the cli requires using valid json :). — Grzesiek Danowski, Nov 14 '18 at 10:03

front_end_dev · Answer 1 · 2018-11-14T10:20:20.273

0

The input that you pass is not a valid JSON structure that's why JSON.parse has shown parsing error.

var validInput = '[{"name":"joe","age":19}]';
console.log(JSON.parse(validInput));

edited Nov 14 '18 at 10:20

answered Nov 14 '18 at 09:54

front_end_dev

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you probably meant `var validInput = '[{"name":"joe","age":19}]';`? – Kaddath Nov 14 '18 at 10:00
So should I force the user to follow the json syntax while passing input? Isnt there a way to convert the input type to [object Array] directly? – Endemic Nov 14 '18 at 10:02
@Endemic You have to write your custom logic then to parse this string and create an valid json. – front_end_dev Nov 14 '18 at 10:05
@Kaddath yes. Sorry i miss the quotes `'`. Edit answer – front_end_dev Nov 14 '18 at 10:05
you need double quotes for `"joe"` too ;) – Kaddath Nov 14 '18 at 10:13

O.O · Answer 2 · 2018-11-14T10:40:41.673

0

Run Code Snippet.

var obj = new Object({name:'joe', age:19});
console.log(typeof obj);

edited Nov 14 '18 at 10:40

answered Nov 14 '18 at 09:55

O.O

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When I follow your method, the type changes to object but when I console.log(obj) it returns the output - [String: '[{name:\'arjun\',age:19}]'] – Endemic Nov 14 '18 at 10:08

score 0 · Answer 3 · answered Nov 14 '18 at 09:58

0

JSON.parse expects keys to be in double quotes. so somehow you have to change the input to this format

JSON.parse([{"name":"joe", "age":"19"}])

and the output would be

answered Nov 14 '18 at 09:58

Asim Khan

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So should I force the user to follow the json syntax while passing input? Isnt there a way to convert the input type to [object Array] directly? – Endemic Nov 14 '18 at 10:01

Kaddath · Answer 4 · 2018-11-14T11:58:16.960

You can still try these regexes, that will convert your string into valid JSON. Be careful that it's not perfect, this version only accepts letters and numbers as keys for objects, while other characters can be valid too for object keys. You have to modify this part [a-zA-Z0-9] to improve it if you know a bit of regex..

var str = "[{name:'joe', age:19}, {'name':'jack', age:21}, {\"name\":\"jane\", age:23}]", validJson, obj;
console.log('original string: ', str);

validJson = str.replace(/({\s*|,\s*)'?([a-zA-Z0-9]+)'?(\s*:)/g, '$1"$2"$3').replace(/(:\s*)'(.*?)'(\s*,|\s*})/g, '$1"$2"$3');
console.log('modified string: ', validJson);

obj = JSON.parse(validJson);
console.log('decoded from JSON: ', obj);

EDIT: regex updated to support object keys defined with simple quotes (2nd object). NOTE: it keeps already well formatted JSON as it is (3rd object).

score 0 · Answer 5 · answered Jul 13 '21 at 04:22

0

One solution is to use eval, e.g.

> eval("[{name:'joe', age:19}]")
[ { name: 'joe', age: 19 } ]

answered Jul 13 '21 at 04:22

Jianwu Chen

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How to convert an input of type string into type object array in node js

5 Answers5