Correct way to loop through an JSON object [duplicate] - json

Question

This question already has answers here:
Unable to iterate through JSON array
(3 answers)
Closed 6 years ago.
Since there seems nobody is able to find a solution for my problem, I would like to ask my question in a different way:
What should be the correct way to loop through the games section of the following object:
[
{
"_id": "5710b0ddab8b724011705037",
"username": "test",
"name": "testuser",
"__v": 0,
"library": {
"games": [
{
"platform": [
"17",
"94"
],
"name": "Simcity",
"id": "37620"
},
{
"platform": [
"146",
"20"
],
"name": "destiny",
"id": "36067"
}
],
"platforms": [
{
"name": "Xbox360",
"id": "20"
},
{
"name": "PC",
"id": "94"
}
]
}
}
]
This object is fetched out through mongoose out of a MongoDB, all happens in the API section of my NodeJS application:
.get('/test', function(req, res){
User.findOne({"username": req.decoded.username}, function(err, user){
// trying to loop here
});
})
I have tried everything I find, but I cannot get it to work, so I wonder what ways you use to do this, without cluttering your vision with my (maybe wrong) ways and errors...

Answer 1

Use for...in to loop through Javascript/JSON objects
for (variable in object) {...
}
for...in documentation
Use forEach to loop through Javascript/JSON arrays
arr.forEach(callback[, thisArg])
forEach documentation

Answer 2

Updated Answer:
Your edit markedly changes the structure of the data compared to your original question.
Now, you have an array containing one entry, which has library, which has games, so you reference it (assuming user points to the whole thing) as user[0].library.games. E.g.:
user[0].library.games.forEach(function(entry) {
// Use `entry` here
});
var user = [{
"_id": "5710b0ddab8b724011705037",
"username": "test",
"name": "testuser",
"__v": 0,
"library": {
"games": [{
"platform": [
"17",
"94"
],
"name": "Simcity",
"id": "37620"
}, {
"platform": [
"146",
"20"
],
"name": "destiny",
"id": "36067"
}],
"platforms": [{
"name": "Xbox360",
"id": "20"
}, {
"name": "PC",
"id": "94"
}]
}
}];
user[0].library.games.forEach(function(entry) {
log(entry.name);
});
function log(msg) {
var p = document.createElement('p');
p.appendChild(document.createTextNode(msg));
document.body.appendChild(p);
}
Original Answer:
games is an array, assuming you have o referencing that object, you can reference it from o.user.library.games.
There are lots of ways to loop over arrays (see this answer for a list); one of them is forEach:
o.user.library.games.forEach(function(entry) {
// Use `entry` here, e.g. `entry.name`, `entry.id`, etc.
});
E.g.:
var o = {
"user": {
"name": "testuser",
"library": {
"platforms": [{
"id": "20",
"name": "Xbox360"
}, {
"id": "94",
"name": "PC"
}],
"games": [{
"id": "37620",
"name": "Simcity",
"platform": [
"17",
"94"
]
}, {
"id": "36067",
"name": "destiny",
"platform": [
"146",
"Xbox360"
]
}]
}
}
};
o.user.library.games.forEach(function(entry) {
log(entry.name);
});
function log(msg) {
var p = document.createElement('p');
p.appendChild(document.createTextNode(msg));
document.body.appendChild(p);
}
From your comment below, it sounds like the structure may not be quite as you quoted it in the question. You can use node-inspector to debug your NodeJS code, set a breakpoint at the beginning of where you want to loop, and inspect the variable you have referring to the object. That will show you its structure. It's very easy to install (npm install -g node-inspector) and use (node-debug your-main-file.js).