How to convert a string with arrays to an array

Question

How do I convert this piece of response into a valid array?
I want to perform an Object.map on the data:

var user_roles = "['store_owner', 'super_admin']";

This is not a valid JSON so I can't use JSON.parse

how do you produce this string? maybe a [JSON](http://json.org/) compliant string would be easier to parse. — Nina Scholz, Jul 18 '18 at 08:28
Though this string can't be JSON-parsed, it _is_ valid JS. Maybe you could use `eval`? — Berry M., Jul 18 '18 at 08:31
right, `eval` works, but it's a workaround. better generate a string which does not have a custom format. — Nina Scholz, Jul 18 '18 at 08:33
This is not a duplicate of that question, as it is not a valid JSON — Adelin, Jul 19 '18 at 05:26

score 8 · Accepted Answer · edited Jul 18 '18 at 08:46

8

Right, most answers posted here suggest using JSON.parse and then get downvoted 3 times before getting deleted. What people overlook here is the lack of JSON-compliant quotation. The string IS, however, valid JavaScript. You can do the following:

const obj = {
  thing: "['store_owner', 'super_admin']",
  otherThing: "['apple', 'cookies']"
}

for (const key in obj) {
  const value = obj[key];
  obj[key] = eval(value);
}

console.log(obj);

Output will be a valid javascript object:

{"thing":["store_owner","super_admin"],"otherThing":["apple","cookies"]}

Be careful with eval(), though! javascript eval() and security

You can try it here: https://es6console.com/jjqvrnhg/

edited Jul 18 '18 at 08:46

Federico klez Culloca

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answered Jul 18 '18 at 08:44

Berry M.

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**[Why is using the JavaScript eval function a bad idea?](https://stackoverflow.com/q/86513/4281779)** – Zakaria Acharki Jul 18 '18 at 08:47
Hence the security warning I added. This entire case smells of a bad idea, though! – Berry M. Jul 18 '18 at 08:49
1

@ZakariaAcharki yes, yes... You're just adding noise to the already mentioned security issues (Berry linked a similar question)... An alternative solution would be more useful instead. – CPHPython Jul 18 '18 at 08:51
It feels like there must be a better way.. – Adelin Jul 18 '18 at 08:52
3

Even with the warning `eval()` should not be considered. The input, which the OP describes as “part of a response” is clearly out of their control. Those warnings apply specifically to this situation. – Mark Jul 18 '18 at 09:04
1

It works as long as the string doesn't contain any escaped single quote : `"['store_owner', 'super_admin\'s right']"` – Guillaume Georges Jul 18 '18 at 09:06
1

I agree, @MarkMeyer. The best solution, in this case, would of course be reconsidering the entire setup that lead to this situation. You'll never end up covering all edge-cases, like Guillaume's. – Berry M. Jul 18 '18 at 09:09

score 3 · Answer 2 · answered Jul 18 '18 at 09:07

I took the polyfill for JSON.parse I found here

And replaced the meaning of a string to consist of '' single quote notation:

/*
    json_parse.js
    2016-05-02
    Public Domain.
    NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
    This file creates a json_parse function.
        json_parse(text, reviver)
            This method parses a JSON text to produce an object or array.
            It can throw a SyntaxError exception.
            The optional reviver parameter is a function that can filter and
            transform the results. It receives each of the keys and values,
            and its return value is used instead of the original value.
            If it returns what it received, then the structure is not modified.
            If it returns undefined then the member is deleted.
            Example:
            // Parse the text. Values that look like ISO date strings will
            // be converted to Date objects.
            myData = json_parse(text, function (key, value) {
                var a;
                if (typeof value === "string") {
                    a =
/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)Z$/.exec(value);
                    if (a) {
                        return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],
                            +a[5], +a[6]));
                    }
                }
                return value;
            });
    This is a reference implementation. You are free to copy, modify, or
    redistribute.
    This code should be minified before deployment.
    See http://javascript.crockford.com/jsmin.html
    USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU DO
    NOT CONTROL.
*/

/*jslint for */

/*property
    at, b, call, charAt, f, fromCharCode, hasOwnProperty, message, n, name,
    prototype, push, r, t, text
*/

var json_parse = (function () {
    "use strict";

// This is a function that can parse a JSON text, producing a JavaScript
// data structure. It is a simple, recursive descent parser. It does not use
// eval or regular expressions, so it can be used as a model for implementing
// a JSON parser in other languages.

// We are defining the function inside of another function to avoid creating
// global variables.

    var at;     // The index of the current character
    var ch;     // The current character
    var escapee = {
        "\"": "\"",
        "\\": "\\",
        "/": "/",
        b: "\b",
        f: "\f",
        n: "\n",
        r: "\r",
        t: "\t"
    };
    var text;

    var error = function (m) {

// Call error when something is wrong.

        throw {
            name: "SyntaxError",
            message: m,
            at: at,
            text: text
        };
    };

    var next = function (c) {

// If a c parameter is provided, verify that it matches the current character.

        if (c && c !== ch) {
            error("Expected '" + c + "' instead of '" + ch + "'");
        }

// Get the next character. When there are no more characters,
// return the empty string.

        ch = text.charAt(at);
        at += 1;
        return ch;
    };

    var number = function () {

// Parse a number value.

        var value;
        var string = "";

        if (ch === "-") {
            string = "-";
            next("-");
        }
        while (ch >= "0" && ch <= "9") {
            string += ch;
            next();
        }
        if (ch === ".") {
            string += ".";
            while (next() && ch >= "0" && ch <= "9") {
                string += ch;
            }
        }
        if (ch === "e" || ch === "E") {
            string += ch;
            next();
            if (ch === "-" || ch === "+") {
                string += ch;
                next();
            }
            while (ch >= "0" && ch <= "9") {
                string += ch;
                next();
            }
        }
        value = +string;
        if (!isFinite(value)) {
            error("Bad number");
        } else {
            return value;
        }
    };

    var string = function () {

// Parse a string value.

        var hex;
        var i;
        var value = "";
        var uffff;

// When parsing for string values, we must look for " and \ characters.

        if (ch === "\'") {
            while (next()) {
                if (ch === "\'") {
                    next();
                    return value;
                }
                if (ch === "\\") {
                    next();
                    if (ch === "u") {
                        uffff = 0;
                        for (i = 0; i < 4; i += 1) {
                            hex = parseInt(next(), 16);
                            if (!isFinite(hex)) {
                                break;
                            }
                            uffff = uffff * 16 + hex;
                        }
                        value += String.fromCharCode(uffff);
                    } else if (typeof escapee[ch] === "string") {
                        value += escapee[ch];
                    } else {
                        break;
                    }
                } else {
                    value += ch;
                }
            }
        }
        error("Bad string");
    };

    var white = function () {

// Skip whitespace.

        while (ch && ch <= " ") {
            next();
        }
    };

    var word = function () {

// true, false, or null.

        switch (ch) {
        case "t":
            next("t");
            next("r");
            next("u");
            next("e");
            return true;
        case "f":
            next("f");
            next("a");
            next("l");
            next("s");
            next("e");
            return false;
        case "n":
            next("n");
            next("u");
            next("l");
            next("l");
            return null;
        }
        error("Unexpected '" + ch + "'");
    };

    var value;  // Place holder for the value function.

    var array = function () {

// Parse an array value.

        var arr = [];

        if (ch === "[") {
            next("[");
            white();
            if (ch === "]") {
                next("]");
                return arr;   // empty array
            }
            while (ch) {
                arr.push(value());
                white();
                if (ch === "]") {
                    next("]");
                    return arr;
                }
                next(",");
                white();
            }
        }
        error("Bad array");
    };

    var object = function () {

// Parse an object value.

        var key;
        var obj = {};

        if (ch === "{") {
            next("{");
            white();
            if (ch === "}") {
                next("}");
                return obj;   // empty object
            }
            while (ch) {
                key = string();
                white();
                next(":");
                if (Object.hasOwnProperty.call(obj, key)) {
                    error("Duplicate key '" + key + "'");
                }
                obj[key] = value();
                white();
                if (ch === "}") {
                    next("}");
                    return obj;
                }
                next(",");
                white();
            }
        }
        error("Bad object");
    };

    value = function () {

// Parse a JSON value. It could be an object, an array, a string, a number,
// or a word.

        white();
        switch (ch) {
        case "{":
            return object();
        case "[":
            return array();
        case "\'":
            return string();
        case "-":
            return number();
        default:
            return (ch >= "0" && ch <= "9")
                ? number()
                : word();
        }
    };

// Return the json_parse function. It will have access to all of the above
// functions and variables.

    return function (source, reviver) {
        var result;

        text = source;
        at = 0;
        ch = " ";
        result = value();
        white();
        if (ch) {
            error("Syntax error");
        }

// If there is a reviver function, we recursively walk the new structure,
// passing each name/value pair to the reviver function for possible
// transformation, starting with a temporary root object that holds the result
// in an empty key. If there is not a reviver function, we simply return the
// result.

        return (typeof reviver === "function")
            ? (function walk(holder, key) {
                var k;
                var v;
                var val = holder[key];
                if (val && typeof val === "object") {
                    for (k in val) {
                        if (Object.prototype.hasOwnProperty.call(val, k)) {
                            v = walk(val, k);
                            if (v !== undefined) {
                                val[k] = v;
                            } else {
                                delete val[k];
                            }
                        }
                    }
                }
                return reviver.call(holder, key, val);
            }({"": result}, ""))
            : result;
    };
}());

console.log(json_parse("['store_owner', 'super_admin']"));

Andria · Answer 3 · 2018-07-18T08:45:47.017

-2

Make it JSON compliant

JSON.parse(user_roles.replace(/(?<!\\)'/g,'"')

This works by fixing the reason why your code can't be parsed by JSON. That reason is that JSON doesn't let you use single quotes (') so we change them to Double Quotes (")

EDIT:

I made it so that when a ' is preceded by a \ it will not be replaced with a ".

edited Jul 18 '18 at 08:45

answered Jul 18 '18 at 08:33

Andria

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`str = "['store_owner', 'super_ad\'min']"`, `JSON.parse(str.replace(/'/g,'"'))` => `unexpected token m` – Adelin Jul 18 '18 at 08:35
That didn't seem to be a problem the OP would likely have but I have made it so in case of that, it shall still work. – Andria Jul 18 '18 at 08:46
I still get the exact same error – Adelin Jul 18 '18 at 08:47
@Adelin It has to be preceded by a `\ ` in a string, just placing `\'` returns `'` you need `\\'` – Andria Jul 18 '18 at 08:52
1

I think this is the best solution since now... – Zakaria Acharki Jul 18 '18 at 09:20

How to convert a string with arrays to an array

3 Answers3

Make it JSON compliant

EDIT:

Linked