CODEWITHSUNDEEP
javascript
user1243746
user1243746

Reputation:

Stringify only a field in JavaScript

I would want that at passing an object at JSON.Stringify, it checks if it has a field like "val" for stringify only that field, else been stringfied everything.

Is possible to change JSON.Stringify to stringy only a determined field?

Upvotes: 0

Views: 120

Answers (3)

KooiInc
KooiInc

Reputation: 122956

You can use a replacer method.

var myObj = {a:1,b:2,c:3,d:4,e:5}
   ,myObjStr = JSON.stringify(myObj,censor);

//=> myObjStr now: "{"a":1,"b":2,"c":3}"

function censor(key,val){
  return !key ? val : val>3 ? undefined : val;
}

If I understood your question right, in your case you could use something like:

var myObj = {a:{val:1},b:{val:2},c:3,d:null,e:'noval'}
   ,myObjStr = JSON.stringify(
                       myObj,
                       function(key,val){ 
                         return !key 
                                ? val 
                                : val && val.val 
                                  ? JSON.stringify(val) 
                                  : undefined;
                       });
 //=> myObjStr: {"a":"{\"val\":1}","b":"{\"val\":2}"}

See also

Upvotes: 0

Pavel Strakhov
Pavel Strakhov

Reputation: 40512

It's quite simple:

function my_json_stringify(obj) {
  return JSON.stringify("val" in obj ? obj.val : obj);
}

console.log(my_json_stringify({ a: 1, b: 2})); // => {"a":1,"b":2}
console.log(my_json_stringify({ val: { a : 3, b: 4 }, other: 5}));
  // => {"a":3,"b":4}

You generally must not modify system functions. It's very bad idea. But if you have to do it, it can be done like that:

JSON.original_stringify = JSON.stringify;

JSON.stringify = function(obj) {
  return JSON.original_stringify(obj.val ? obj.val : obj);
}

At least, it works in Firefox. But I don't know if it will work on any other JS implementation or not.

Upvotes: 0

phant0m
phant0m

Reputation: 16905

You need to watch out for falsy values:

function my_json_stringify(obj) {
  return JSON.stringify(obj.hasOwnProperty("val") ? obj.val : obj);
}

Otherwise, it is going to provide wrong results for things like

{
    val: ""
}

You may need to include some cross-browser solution for hasOwnProperty as shown here.

Upvotes: 1

Related Questions