I feel like I have to be missing something simple here. I want to use JSON.parse to convert a string to a JSON object. I've been playing around with this simple example.
JSON.stringify({hi:'"bye"'})
//returns "{"hi":"\"bye\""}"
JSON.parse(JSON.stringify({hi:'"bye"'}))
//returns Object {hi: ""bye""}
JSON.parse("{"hi":"\"bye\""}")
//returns SyntaxError: Unexpected identifier
JSON.parse('{"hi":"\"bye\""}')
//Unexpected token b
My question is what is the difference between passing in the stringify return manually versus passing the return of stringify directly to parse? Mu ultimate goal is to be able to parse a JSON string into a JSON object where the values may contain double quotes.
Thanks for the help.
You have to escape the backslashes and quotation marks when you put the string representation of the object in a string using quotation mark as delimiter:
JSON.parse("{\"hi\":\"\\\"bye\\\"\"}")
When you use apostrophes as string delimiter you don't have to escape quotation marks (but you would have to escape apostrophes if you had any):
JSON.parse('{"hi":"\\"bye\\""}')
Related
When I try to JSON.parse("foo"), I get an Error:
Uncaught SyntaxError: Unexpected token o in JSON at position 1
at JSON.parse (<anonymous>)
at <anonymous>:1:6
But, when I use JSON.parse('"foo"'), I can get the result as expected:
const value = JSON.parse('"foo"');
console.log(value)
So why does this happen?
You can find what makes valid JSON at json.org. JSON can represent null, booleans, numbers, strings, arrays and objects. For strings, they must be enclosed in double quotes.
JSON itself is a string format, so when you specify a string in JSON format, you need:
quotes to tell JavaScript you are specifying a string literal. Those quotes are not part of the string value itself; they are just delimiters.
double-quotes inside that string literal to follow the JSON syntax for the string data type.
So here are some examples of correct arguments for JSON.parse:
JSON.parse("true")
JSON.parse("false")
JSON.parse("null")
JSON.parse("42")
JSON.parse("[13]")
JSON.parse('"hello"')
JSON.parse('{"name": "Mary"}')
But not:
JSON.parse("yes")
JSON.parse("no")
JSON.parse("none")
JSON.parse('hello')
JSON.parse({"name": "Mary"})
Because the argument will be cast to string when it is not, the following will also work, but it is confusing (and useless):
JSON.parse(true)
JSON.parse(false)
JSON.parse(null)
JSON.parse(42)
This happens because JSON.parse() gives a value back by formatting the string given using the syntaxis to declare values in Javascript. Therefore using foo naked would be like casting an undefined variable.
Notice also that the notation uses double quotes " instead of single ones '. That's why JSON.parse('"foo"') works but JSON.parse("'foo'") won't.
I have this string that I want to convert to an JSON object, the problem is that one of the fields of the object is a regex:
"{
\"regex\": /^([a-zA-Z0-9_\\.\\-\\+%])+\\#(([a-zA-Z0-9\\-])+\\.)+([a-zA-Z0-9]{2,4})+$/,
\"alertText\": \"test\"
}"
Is there a way to get the JavaScript object without doing hundreds of replaces?
EDIT: I use the following code to store the correct serialized version of the original object from Stringifying a regular expression?:
RegExp.prototype.toJSON = function() { return this.source; };
Then I could modify the content of the string:
{"regex":"^([a-zA-Z0-9_\\.\\-\\+%])+\\#(([a-zA-Z0-9\\-])+\\.)+([a-zA-Z0-9]{2,4})+$","alertText":"* {{alertText}}"}
So I can use it as a template, and then, when needed, JSON.parse the string to get a new object.
Simply ensure that your regex value is enclosed with quotes to force it to be a string value:
"{
\"regex\": \"/^([a-zA-Z0-9_\\.\\-\\+%])+\\#(([a-zA-Z0-9\\-])+\\.)+([a-zA-Z0-9]{2,4})+$/\",
\"alertText\": \"test\"
}"
Then, this will parse as a JSON object correctly and you can get the regex out later to create your regex from it.
If you require the slashes double escaped for your regex purposes, then...
"{
\"regex\": \"/^([a-zA-Z0-9_\\\\.\\\\-\\\\+%])+\\\\#(([a-zA-Z0-9\\\\-])+\\\\.)+([a-zA-Z0-9]{2,4})+$/\",
\"alertText\": \"test\"
}"
Solution:
One alternative solution whould be to change/reformat your JSON string, you will simply need to :
Change the enclosing double quotes " with a single quote '.
And use only one backslash \ for escaping.
This is a working DEMO:
var text = '{"regex": "/^([a-zA-Z0-9_\.\-\+%])+\#(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/", "alertText": "test"}';
var obj=JSON.parse(text);
console.dir(obj);
document.write(obj.regex);
document.write("<br>"+obj.alertText);
The short answer is No.
Answers so far rely on being able to change the string at source. If you can do that, great, but as per the OP, you can't parse the JSON with a regex value using a stock JSON.parse(), even with a reviver function.
What I am trying to do is simple. Parse this array holding json objects into a Javascript array.
var merchantsJson = JSON.parse('[{"id":61693,"name":"Más"},{"id":61690,"name":"\u0027\u0022\u003C/div\u003E"}]');
But the unicode character \u003C seems to be breaking the parser. In the chrome console I see "Uncaught SyntaxError: Unexpected token <"
A little more info. The above is what the code is evaluated to. In reality the code contains a jsp expression.
var merchantsJson = JSON.parse('${jsonArr}');
If I remove the single quotes, there is no issue, but eclipse give me an "missing semicolon" error message. Is it possible to parse the array with the quotes as I am trying to do?
The interpolation of ${jsonArr} is already a JavaScript object. When you wrap it in '${jsonArr}' this turns it into a string and you have to use JSON.parse.
There's no need to make it a string. You can just do var merchantsArray = ${jsonArr}. JSON constructs are already interoperable with JavaScript code.
Because there's an extra " in your string literal that is encoded by \u0022:
> '[{"id":61693,"name":"Más"},{"id":61690,"name":"\u0027\u0022\u003C/div\u003E"}]'
[{"id":61693,"name":"Más"},{"id":61690,"name":"'"</div>"}]
In short, your JSON in the string is invalid. You would need to escape the unicode escape sequences for the quotes in the string literal ("'\u0022</div>"), by using
JSON.parse('[{"id":61693,"name":"Más"},{"id":61690,"name":"\u0027\\u0022\u003C/div\u003E"}]'
// ^
or escape the quote character ("'\"</div>"):
JSON.parse('[{"id":61693,"name":"Más"},{"id":61690,"name":"\u0027\\\u0022\u003C/div\u003E"}]');
// ^^
However, there actually is no need to use JSON at all. Just output a JS array literal into your code:
var merchantsJson = ${jsonArr};
Try to replace \u with \\u. If you don't, JSON parser receives already decoded Unicode, which created polluted JSON.
It's not because of \u003C, rather the \u0022 character is causing the issue, since it's a quotation mark and JavaScript treats it literally ending the string.
You need to escape that character: \\u0022 .
you have to use special character in your JSON string, you can escape it using \ character.
you need to replace \ with \\.
[{\"id\":61693,\"name\":\"Más\"},{\"id\":61690,\"name\":\"\\u0027\\u0022\\u003C/div\\u003E\"}]
I am trying to pass a JSON string to a C# .exe as a command line argument, from Javascript as a node.js child-process. For the sake of argument my JSON looks something like this:
string jsonString = '{"name":"Tim"}'
The issue with passing this as a C# arg is that the double quotation marks must be retained if I hope to parse it in the C# code. As such, what I need to pass into the C# command line needs to look something like this, where I escape the double quotation mark:
string jsonStringEscaped = '{\"name\":\"Tim\"}'
The motivation for doing this is that it allows me to maintain a consistent object structure across the two languages, which is obviously highly desirable for me.
In order to achieve this, I am attempting to use the Javascript .replace() method prior to sending the argument to the C#, and to do this I use a simple RegEx:
string jsonStringEscaped = jsonString.replace(/\"/g,"\\\"")
Unfortunately, this returns something of the form '{\\"name\\":\\"Tim\\"}' which is useless to me.
I have tried variations on this:
string jsonStringEscaped = jsonString.replace(/\"/g,"\\ \"")
\\ returns '{\\ "name\\ ":\\ "Tim\\ "}'
string jsonStringEscaped = jsonString.replace(/\"/g,"\\\\")
\\ returns '{\\\\name\\\\:\\\\Tim\\\\}'
string jsonStringEscaped = jsonString.replace(/\"/g,"\\\")
\\ is invalid
string jsonStringEscaped = jsonString.replace(/\"/g,"\\\ ")
\\ returns '{\\ name\\ :\\ Tim\\ }'
I have tried variations where the second .replace() argument is contained within single quotation marks '' rather than double quotation marks "" with no success.
Can anyone tell me what I am doing wrong? Better yet, can anyone suggest a more efficient method for doing what I am trying to achieve?
Unless I'm misreading you, I think you're just trying to escape a character that doesn't need to be escaped in your regex (").
var jsonString = '{"name":"Tim"}'
var escaped = jsonString.replace(/"/g, '\\"');
// escaped == "{\"name\":\"Tim\"}"
I ran two pieces of javascript codes in a online JS running platform:Website Link
pets = '{'pet_names':[{"name":"jack"},{"name":"john"},{"name":"joe"}]}';
var arr = JSON.parse(pets);
alert(arr.pet_names[1].name);
Code with double quotes ("pet_names") would be OK but with single quotes('pet_names') would remind a error:"Unexpected identifier"
pets = '{"pet_names":[{"name":"jack"},{"name":"john"},{"name":"joe"}]}';
var arr = JSON.parse(pets);
alert(arr.pet_names[1].name);
So, why do it would happen?
In JSON only double quotes are valid.
You can find the standard on JSON.org
A value can be a string in double quotes, or a number, or true or
false or null, or an object or an array. These structures can be
nested.
In other words, no strings in single quotes.
The first one didn't work because you have a syntax error where you try to define your string literal
you probably wanted
pets = '{\'pet_names\':[{"name":"jack"},{"name":"john"},{"name":"joe"}]}';
notice the quotes are escaped.
Now if you used that string in the json parser you would still get an error(SyntaxError: Unexpected token ') because keys in JSON must be defined with double quotes, using single quotes is valid for defining JavaScript object literals which is separate from JSON.