Node.js - Parse simple JSON object and access keys and values

Question

I am new to Node and struggling to access a simple JSON object. My request.body will have JSON content similar to the following:

{
    "store_config": [
        {
            "name": "hello",
            "name2": "world"
        }
    ]
}

The "store_config" value will always be present, however the keys and values within could be anything.

How can I iterate through the keys and values to access each? I would also like to process each in an asynchronous manner.

Appreciate any thoughts or direction.

UPDATE

console.log(typeof(request.body));

Returns: Object

parsedBody = JSON.parse(request.body);

returns:

SyntaxError: Unexpected token o
    at Object.parse (native)

UPDATE 2 - Further debug:

When I try to iterate through the array, there is only a single value:

request.body.store_config.forEach(function(item, index) {
  console.log(index);
  console.log(request.body.store_config[index]);

});

returns:

0
{ name: 'hello', name2: 'world' }

"I would also like to process each in an asynchronous manner." Uhm... why? — Tomalak
– Tomalak, Commented Nov 11, 2012 at 18:06
FYI, node runs in single thread, so the asynchronous is not the same as in multi-threading programming. When you make a async call with native async procedure like fs.*, it will register a event handler to the event-loop to wait for job to be done. In other cases, you just register a event handler to process.nextTick event, which will callback at each tick, and your code run in series not parallel. — xiaoyi
– xiaoyi, Commented Nov 11, 2012 at 18:19

Michelle Tilley · Accepted Answer · 2012-11-11 18:08:35Z

18

If request.body is already being parsed as JSON, you can just access the data as a JavaScript object; for example,

request.body.store_config

Otherwise, you'll need to parse it with JSON.parse:

parsedBody = JSON.parse(request.body);

Since store_config is an array, you can iterate over it:

request.body.store_config.forEach(function(item, index) {
  // `item` is the next item in the array
  // `index` is the numeric position in the array, e.g. `array[index] == item`
});

If you need to do asynchronous processing on each item in the array, and need to know when it's done, I recommend you take a look at an async helper library like async--in particular, async.forEach may be useful for you:

async.forEach(request.body.store_config, function(item, callback) {
  someAsyncFunction(item, callback);
}, function(err){
  // if any of the async callbacks produced an error, err would equal that error
});

I talk a little bit about asynchronous processing with the async library in this screencast.

answered Nov 11, 2012 at 18:08

Michelle Tilley

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7 Comments

Aurelia Over a year ago

This only applies when using connect/express with bodyParser.

Ben Over a year ago

@brandon-tilley Many thanks. How can I confirm if my request.body is being parsed as JSON already? If I output the store_config, it is an object: console.log(typeof(request.body.store_config)); console.log(request.body.store_config); object [ { name: 'hello', name2: 'world' } ]

Michelle Tilley Over a year ago

If it's "object," then it has been parsed--parsing turns a string into an object. (If it was a string, trying to do request.body.store_config would give an error.)

Ben Over a year ago

When I try to iterate through the array, there is only a single value:

request.body.store_config.forEach(function(item, index) {   console.log(index);   console.log(request.body.store_config[index]);    });

returns - 0 { name: 'hello', name2: 'world' }

Linus Thiel Over a year ago

@Ben: That seems correct, as you have one item in your example -- one object with the two properties name and name2.

|

Lucas Azevedo · Accepted Answer · 2015-11-09 20:29:33Z

2

Something like this:

config = JSON.parse(jsonString);
for(var i = 0; i < config.store_config.length; ++i) {
   for(key in config.store_config[i]) {
      yourAsyncFunction.call(this, key, config.store_config[i][key]);
   }
}

edited Nov 9, 2015 at 20:29

Lucas Azevedo

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answered Nov 11, 2012 at 18:07

Vyacheslav Voronchuk

2,46321 silver badges17 bronze badges

Comments

Aurelia · Accepted Answer · 2012-11-11 18:09:53Z

-1

To convert this sting to an actual object, use JSON.parse. You can iterate though Javascript objects like you would with an array.

config = JSON.parse(string).store_config[0]
foreach (var key in config) {
    value = config[key]
}

answered Nov 11, 2012 at 18:09

Aurelia

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