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I have an unusual Javascript array with a length of 0, but if I expand the array I can see it contains multiple nested arrays with the same property, and eventually an Array containing an object. I've never seen this type of array / object before.
This is a sudo code version (as far I can read it):
[NaN: [{foo:'barr'}]]
But constructing an object like that would cause an error. Can anyone explain what it is?
This is a screen shot of what it looks like console logged in Chrome:
And console logged in Firefox:
It looks like, you have 'NaN' as key, which is possible (arrays are objects), because you may have calculated the index, which goes wrong.
var array = [];
array['x' * 3] = 'value'; // index/key is NaN
console.log(array);
console.log(array.NaN);
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As the title suggests, how do I make a new object containing the 7 first keys of another object using JS? :) This is the structure of the object I would like to copy the data from.
{"data":[{"id":2338785,"team1":{"id":10531,"name":"Just For Fun"},"team2":{"id":10017,"name":"Rugratz"},"result":"2 - 0","event":{"name":"Mythic Cup 5","id":5148},"format":"bo3","stars":0,"date":1578279271000},....],"last_update":1578329378792}
Let's say there are 100 keys like this one, and I only want to copy the 7 first ones into a new object in JS.
Well technically, you have only 2 keys in the given Object but if you mean the data object, here's what you can do.
const MyNewObject = Object.entries(YourObject)
const results = []
and a simple for loop
MyNewObject.forEach((pair,i) => {
// for the 8th item it breaks and doesn't push it to results array
if ( i === 7 ) break;
results.push(pair)
}
OR u use slice instead :
// a little bit neater , and u call remove the empty results array above
const thisNewResult = MyNewObject.slice(0,6)
and finally the results is an array of key value pairs and you should do this code to make a new object from the results entries
const finalResults = Object.fromEntries(results)
Please notice that this may not be the Order you want since Object.Entries gives you the same order as the order of for in loop (for more info visit Elements order in a "for (… in …)" loop)
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I made an array for a raffle system using node.js and discord.js which has this data set.
[{"author":"Name","rafflename":"RAFFLE","amount":"10","entries":"[]"}]
When someone tries to enter the raffle I'd like to make another JSON array inside the entries tag.
The problem i face is when i use raffles[0].entries.push({ 'username': 'example', 'user_id': '1' });
It returns an error: raffles[0].entries.push is not a function
I assume this is because it is looking for the array raffles[0].entries.push which does not exist. But I've only ever used the push command. So I am not sure how to fix this issue.
Move your entries [] out of double quotes, i.e. Use "entries" :[]
You are trying to push to a string instead of array
You have to cast entries to Array first.
const raffles = [{"author":"Name","rafflename":"RAFFLE","amount":"10","entries":"[]"}]
// cast entries to Array
raffles[0].entries = JSON.parse(raffles[0].entries)
// now you can push them
raffles[0].entries.push('test')
console.log(raffles)
It isn't working because you have "" around the properties inside of your object. you can fix this by either removing the "" or doing this:
raffles[0]['entries'].push(//your code here);
When properties of an object are strings (i.e. when they have quotes around them) you must access that property using "dot notation"
eg:
var object = {"property":"five"};
console.log(object["property"]); //prints 'five'
console.log(object.property); //throws an error
Format Your Array according to #Bibberty Comment and do operation
raffles=rafale=[{"author":"Name","rafflename":"RAFFLE","amount":10,"entries":[]}]
raffles[0].entries.push({ 'username': 'example', 'user_id': 1 });
console.log(raffles)
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When trying to push items to an array in javascripts it gives an error, the following pseudo code illustrate what is happening:
var data = new Array();
for(...) {
data[key].push(item[i]);
}
It is showing the following error:
Cannot read property 'push' of undefined
Thanks
If you need a 2d array, you have to initialize each element of the outer array to be an array.
// Have to check every array item, if it's not an array already, make it so
for(...) {
if (!data[key]) {
data[key] = [];
}
data[key].push(item[i]);
}
You could always do the following if you know the number of inner arrays you need:
var data = [[],[],[],[],[],[]];
In your example, since they variable name is key, I'm assuming you actually want an object of arrays. If you know the keys ahead of time, you can use the following literal.
var data = {
myKey1: [],
myKey2: []
}
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I have a json web service that returns simply [].
Then, I have a javascript Object variable json_var that contains this json output. When json returns empty [], json_var is undefined. How do I check from the content of json_var that the json output is empty []?
check for the length of the response. As it was mentioned [] refers to an empty array
var test = [];
console.log(test.length); // returns 0
JSFIDDLE
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I have a text field with id search_json on a form that contains:
{"standard_id":"2","attribute1":["","Stan"],"attribute2":[""],"attribute3":["","Air Force"],"attribute4":["","Bob"],"selected_index":3}
Upon some event, call it a button click, I want to:
1) Read in that JSON and parse it into an object:
search_json = $.parseJSON($("#search_json").val())
2) Remove "attribute1" from the object
delete search_json["attribute1"]
3) Write the JSON back out to the text field:
$("#search_json").val(JSON.stringify(search_json))
I'm kind of surprised it's not working, though. The delete call does nothing. As a matter of fact,
search_json.hasOwnProperty("attribute1")
returns false. And yet I can log the object to console and it is indeed an object with those values. What is going wrong here?
UPDATE: Actually,
search_json.hasOwnProperty("attribute1")
DOES work. But, if I get the attribute name from another text field, like so:
attribute_name = $("#attribute_name").attr("id")
and:
console.log attribute_name
shows "attribute1", then this does NOT work:
search_json.hasOwnProperty(attribute_name)
returns FALSE. Mystifying.
I don't get it. I'm using your fiddle code and everything is correct
http://jsfiddle.net/ddQbe/1/
The final object is:
attribute2: Array[1]
attribute3: Array[2]
attribute4: Array[2]
selected_index: 3
standard_id: "2"
attribute1 was delete correclty
I would try creating a new result_json object.
var result_json = {};
for (var prop in search_json) {
if (prop !== 'attribute1') {
result_json[prop] = search_json[prop];
}
}
$("#search_json").val(JSON.stringify(result_json));