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How to get JSON values of multiple keys of the same name

I have a JSON data set as follows:
{
"content":[],
"layout":[],
"trail":[
{
"content":[
{
"type":"image",
"media":[
{
"type":"image/jpg",
"width":593,
"height":900,
"url":"https://live.staticflickr.com/65535/48208920877_e6b234d3ea_c_d.jpg",
"flickr":{
"flickr-post":"https://www.flickr.com/photos/riketrs/48208920877",
"flickr-album":"https://www.flickr.com/photos/riketrs/albums/72157709130951466"
}
}
]
},
{
"type":"image",
"media":[
{
"type":"image/jpg",
"width":1600,
"height":900,
"url":"https://live.staticflickr.com/2817/33807326532_91013ef6b1_h_d.jpg",
"flickr":{
"flickr-post":"https://www.flickr.com/photos/146758538#N03/33807326532",
"flickr-album":"https://www.flickr.com/photos/146758538#N03/albums/72157681438471236"
}
}
]
}
],
"colors":{
"c0":"#1e1e1d",
"c1":"#78736f",
"c2":"#b2a89f"
}
}
]
}
I would like to console.log the "url" key for each of the images shown here.
(https://live.staticflickr.com/65535/48208920877_e6b234d3ea_c_d.jpg and https://live.staticflickr.com/2817/33807326532_91013ef6b1_h_d.jpg)
I tried some code but I'm very new to JSON in general, I've looked at some other answers to do with JSON but I'm not quite sure how to achieve what I want.
JSFiddle: https://jsfiddle.net/fj6qveh1/1/
I appreciate all advice, including links to other answers that I potentially missed.
Thank you!

url is a property of an object. There can be many of these in a media array. (This data only shows one object per array.) media itself is an property of objects inside the content array.
Use map, and flatMap.
map to return the URL values from the objects in media, and flatMap to return a flat array of the nested arrays returned by map.
const data={content:[],layout:[],trail:[{content:[{type:"image",media:[{type:"image/jpg",width:593,height:900,url:"https://live.staticflickr.com/65535/48208920877_e6b234d3ea_c_d.jpg",flickr:{"flickr-post":"https://www.flickr.com/photos/riketrs/48208920877","flickr-album":"https://www.flickr.com/photos/riketrs/albums/72157709130951466"}}]},{type:"image",media:[{type:"image/jpg",width:1600,height:900,url:"https://live.staticflickr.com/2817/33807326532_91013ef6b1_h_d.jpg",flickr:{"flickr-post":"https://www.flickr.com/photos/146758538#N03/33807326532","flickr-album":"https://www.flickr.com/photos/146758538#N03/albums/72157681438471236"}},{type:"image/jpg",width:1600,height:900,url:"https://live.dummyimage.com/2817/dummy.jpg",flickr:{"flickr-post":"https://www.flickr.com/photos/146758538#N03/33807326532","flickr-album":"https://www.flickr.com/photos/146758538#N03/albums/72157681438471236"}}]}],colors:{c0:"#1e1e1d",c1:"#78736f",c2:"#b2a89f"}}]};
const content = data.trail[0].content;
const urls = content.flatMap(obj => {
return obj.media.map(inner => inner.url);
});
console.log(urls)

The easiest way is to use map function. Given that you are very new to programming (the solution has little to do with JSON itself, since the first step is to parse JSON string to a JavaScript object), it would be better if you try yourself. But you start with
let urls = trail["content"].map(x => x["media"][0]["url"])
for more about map function look here

There is a table in the table so for each table:
for(let i in trail){
var content = trail[i]["content"];
content.forEach(content => content.media.forEach(media => console.log(media.url)))
}

To access object properties, you can use a dot (.), and to access an array element, you use its index in square brackets ([]). So you just keep repeating these steps as necessary until you get to the content you're looking for.
Here's how that looks on a simplified version of your object, using the forEach method of arrays to apply a custom function to each item in the content array:
const json = getJson();
json.trail[0].content.forEach(item=>console.log(item.media[0].url));
function getJson(){
let obj = {
"trail": [{
"content": [
{ "media": [{ "url":"image #65535/48208920877_e6b234d3ea_c_d.jpg" }]},
{ "media": [{"url":"image #2817/33807326532_91013ef6b1_h_d.jpg"}]}
]
}]
};
return obj;
}

Javascript Key/Value Pairing with Arrays

I am trying to wrap my head around how I might accomplish something like this, structurally:
var keywordDataProducts =
[
{"keyword" : "keyword1", "list" : [ "DP1", "DP2" ] },
{"keyword" : "keyword2", "list" : [ "DP1" ] }
];
But of course, without the values being hard coded. For instance, we currently loop through all the DP values (DP1, DP2, DP3, etc..) - which all have 0-M keywords. I'm trying to create an inverse lookup of that, where you can get all DPs that use a particular keyword. I have code that uses the structure above perfectly, but I just need the data to get populated more dynamically.
Do I initialize the var keywordDataProducts = []; declaration with anything in it, or define the structure of it having a keyword and a list (which is an array)? Or do you leave it as an array with nothing about it, and define that when you're adding items?
I've heard associative arrays can be used for a situation like this, but I'm not quite wrapping my head around that at the moment. I've also seen objects with {} usages, but there is no push there and I need an array of keywords, which also contains arrays of DPs (list). Thoughts?

You would do something like this, but you didn't clearly describe what the input look like and what output you're looking for.
function fn (input) {
var ouput = {};
input.forEach( function (DP) {
for (prop in DP) {
if (DP.hasOwnProperty(prop) {
if (output[prop]) {
output[prop].push(DP);
} else {
output[prop] = [DP];
}
}
}
});
return output;
}
This takes this kind of input
[{"alpha":...}, {"beta":..., "delta":...}, {"alpha":..., "gamma":...}]
and returns
{"alpha":[{"alpha":...}, {"alpha":..., "gamma":...}]}, "beta":{"beta":..., "delta":...}, "delta":{"beta":..., "delta":...}, "gamma":{"alpha":..., "gamma":...}}

I don't know how you want your output so I just made an object with each keyword as its own key for the DP values.
var data = [{dp: "dp1", keys: ["key1", "key2", "key3"]}, {dp: "dp2", keys: ["key1", "key2", "key3"]}, {dp: "dp3", keys: ["key1", "key2", "key3"]},];
function keyWordArray(arr) {
var newObj = {};
arr.forEach((obj) => {
obj.keys.forEach((keyVal) => {
if(newObj.hasOwnProperty(keyVal)){
newObj[keyVal].dp.push(obj.dp);
} else {
newObj[keyVal] = {dp:[obj.dp],};
}
});
});
return newObj;
}
document.getElementById("data").innerHTML = JSON.stringify(keyWordArray(data));
<div id="data">
</div>

You can treat objects as associative arrays, and you don't have to use "push" to add a new element.
// Create your object like this
var keywordDataProducts =
{
"keyword1" : { "list" : [ "DP1", "DP2"] },
"keyword2" : { "list" : [ "DP1" ] }
};
// Treat it like an associative array
var keyword1 = keywordDataProducts["keyword1"];
alert("keyword1 = " + keyword1.list.join(", "));
// Add to it like this
keywordDataProducts["keyword3"] = { "list" : ["DP3", "DP4"] };
// See the new object includes your new keyword
alert(JSON.stringify(keywordDataProducts));
// To iterate the keys of your object, you can do something like this
for(var item in keywordDataProducts)
{
if(keywordDataProducts.hasOwnProperty(item))
{
alert(item);
}
}
You can see the fiddle here;
https://jsfiddle.net/gksjtwr6/2/

jQuery getJSON print array where name is string

I have some good practice with using php and mysql, and am now starting with JSON.
I've made a simple json index containing paths to folders, and items inside them:
{ "foldery" : [
{
"foName": "website/img/bg",
"files" : [
"website/img/bg/bg1.jpeg",
"website/img/bg/bg2.jpg",
"website/img/bg/bg3.jpg",
"website/img/bg/bg4.jpeg"
]
},
{
"foName": "website/img/post1",
"files" : [
"website/img/post1/a.jpeg",
"website/img/post1/b.jpg",
"website/img/post1/c.jpeg",
"website/img/post1/d.jpg"
]
}
]
}
Now here is my jquery, for now returning a big mess of data, somewhere including the info about the contents inside:
$.getJSON("nameindex.json", function(data) {
console.log(data);
});
What I would like it to do, in mySql looks like this:
SELECT files FROM foldery WHERE foName = "website/img/post1"
Thus the result, would be an array containing all the files inside post1.
Unfortunately tho, after 2 hours of attempts I have nothing more than the simple console.log code.
Any help would be gladly appreciated

You need to iterate over your array and check forName to equality
function select(o, foName) {
var length = o.foldery.length;
for(var i = 0; i < length; i++){
if (o.foldery[i].foName == foName) {
return o.foldery[i].files;
}
}
}
var result = select(o, "website/img/post1")
console.log(result);
Result
[ 'website/img/post1/a.jpeg',
'website/img/post1/b.jpg',
'website/img/post1/c.jpeg',
'website/img/post1/d.jpg' ]

Get multiple arrays of mongodb documents and merge them for unique values

I need to get all tags, which are stored in an array for multiple documents. I can select all needed documents by:
Collection.find({ 'metadata.tags': { $exists: true } });
The data of the first document could look like
"metadata" : {
"type" : "photo",
"tags" : [
"test",
"anything",
"something",
"more"
]
}
The second one:
"metadata" : {
"type" : "photo",
"tags" : [
"different",
"content",
"something",
"more"
]
}
Some of the elements in the arrays are duplicated. I need just unique values, so the result in this example would have six elements.
I would think of something like this for removing duplicates:
var c = a.concat(b);
var tags = c.filter( function (item, pos) { return c.indexOf(item) == pos; } );
return tags;
But my first problem is how to get access of all arrays, which could be more then just two, as the find() will give me multiple documents. How do I get the arrays of all documents and merge them?
The second problem is to remove duplicates, as my example would just work for two arrays.
Update
I would do something like this:
var tags = [];
Media.find({ 'metadata.tags': { $exists: true } }).forEach(function(doc) {
tags = tags.concat(doc.metadata.tags);
});
var result = tags.filter( function (item, pos) { return tags.indexOf(item) == pos; } );
return result;
Maybe this could be optimized...

To solve your , mongoDB has already provided us a distinct command. Use it like below:
Collection.distinct('metadata.tags')
The above command will give you distinct values from the array. There wont be any duplicate elements. Hence your second problem will also be solved

Null Values in array of objects

I am creating objects when textbox having some values (using ng-blur and textbox.value!==undefined) and then putting these objects in an array (all working fine here).
When I click on checkbox (checkbox model bind with textbox ng-required) I need to delete that particular object having that textbox value.
I am using:
arr.splice(index,1);
to remove that particular object from array (by matching it's name like "monthly" or "quarterly" etc.), but it is creating null at that particular position.
for e.g. [object,object,object]
[
{name:"monthly",
amount:1000 },
{name:"quarterly",
amount:1200 },
{name:"yearly",
amount:1300 }
]
after removing all element it shows [] and when I add another new object it displays [3:object] and it's content as [null,null,null,object];
or
if I remove middle object say name:"quarterly", it shows [object,object] but after adding a new object it display array as [object,object,null,object] with length of array as 4.
Why is there null and how can I remove that from array. (don't want to iterate again to check null).

It is difficult to say why your code creates the null values without have a look to it.
But I can say you that it is not the expected behaviour.
You can see this example to get some inspiration:
var data = [
{name:"monthly",
amount:1000 },
{name:"quarterly",
amount:1200 },
{name:"yearly",
amount:1300 }
];
var newObjectToBeAdded = { name: "daily", amount:"100" }
function showObjects()
{
document.body.innerHTML += data + '<hr>';
}
function deleteObjectByName( objectName )
{
for( var i = 0; i < data.length; i++ )
{
if( data[ i ].name == objectName )
{
data.splice(i, 1);
}
}
}
function addObjectToData( newObject )
{
data.push( newObject );
}
showObjects();
deleteObjectByName( "quarterly" );
showObjects();
addObjectToData( newObjectToBeAdded );
showObjects();
Just to throw a guess out, maybe you are accidentally duplicating the array. Maybe in some point of your code you are doing something like this:
var new_array = original_array.splice( index );
Or creating the new array in the loop you use to find the target object, or using some kind of intermediate array, etc.
Hope it helps!

var arrayWithoutNulls = myArray.filter(function(val) {
if (val) {
return val;
}
});