using the following feed:
http://api.twitter.com/1/statuses/user_timeline.json?screen_name=microsoft&include_rts=1&count=10
I am successfully able to loop through this to get the details I want to display on my html page.
However, I need to check if retweeted_status.user.profile_image_url exists, and I am not sure how to do that?
Currently I am looping through the data where data is returned by jquery-ajax:
data[i].retweeted_status.user.profile_image_url
if data[i].retweeted_status.user.profile_image_url does not exist, it does not return null or undefined, I just get the following error:
cannot read property 'user' of undefined
That error message suggests that either your data[i] or your retweeted_status is undefined, which means your call to get the json is most likely failing. WHen data is returned from Twitter it will aways have a profile image url, because they show an egg-like image for those with none uploaded. You should put this before your for loop:
if (typeof(retweeted_status) != "undefined")
{
//code for what to do with json here
}
I think it's a good answer:
if('key' in myObj)
if (something !== undefined) {
...
}
... or even better:
if (typeof something != "undefined") {
...
}
If you are looping and accessing nesting objects:
if(!data)
return;
while(data.length)
{
var tweet_data = data.shift();
/* do some work */
if(!tweet_data|| !tweet_data.retweeted_status)
continue;
var retweeted_status = tweet_data.retweeted_status;
/* do your other work */
}
This loop no longer needs to use array indexes, which isn't the most efficient unless you specifically need the index for something. Instead, it pops the first element off the array and using that object directly. The loop internals can then check the existence of a property on tweet_data.
I try to avoid using more than 1 level of dereferencing for 2 reasons (like objA.child.property):
1) You can check the existence of an object from the start and if it doesn't exist, jump out or assign default values.
2) Everytime JavaScript needs to access the method property, it first has to find child withing objA and then access property. Could be slow in large loops.
Take a look at $.grep(). It helps you loop through JSON objects. I used it on the link you provided. I used it to loop through the tweets and find the retweeted user images. You can have a look at my code here:
http://jsfiddle.net/q5sqU/7/
Another thing you can do, which has worked for me:
if(retweeted_status) {
// your code
}
Related
I am trying to write a function that takes pokemon’s name as an argument and find out which all pokemon have that name in their “next_evolution” field
Consider the following JSON dataset -
visit https://raw.githubusercontent.com/Biuni/PokemonGO-Pokedex/master/pokedex.json
now for that, I've written the following function:
var infoOfPokemon = function(nameOfPokemon,allPokemon){
for(x in allPokemon){
if(allPokemon[x].next_evolution.includes(nameOfPokemon)){
console.log('pokemons found: '+allPokemon[x].name)
} else{
null
}
}
}
var nameOfPokemon =prompt('enter the name of Pokemon')
infoOfPokemon(nameOfPokemon,pokemonData.pokemon)
but it is returning an error which says
Uncaught TypeError: Cannot read property 'includes' nextEvolution.js:4090 of undefined
One or more of your pokemon does not have a 'next_evolution' field set (for example, the one with id 3 in your file). Hence allPokemon[x].next_evolution evaluates to undefined and you cannot read 'includes' on that.
Check for the existence of next_evolution, first.
if (allPokemon[x].next_evolution &&
allPokemon[x].next_evolution.includes(nameOfPokemon)) { ...
and find out which all pokemon have that name in their “next_evolution” field
That should make you think of filter. You want to filter the list of pokemon to find the matching ones.
But, as already pointed out, you need to be able to return false in your filter predicate if the pokemon you're testing does not have a next_evolution field. You can do that via testing, as suggested in another answer: pokemon.next_evolution && pokemon.next_evolution.includes..., or you can default it, as below: (pokemon.next_evolution || []).includes...
(Note though that both you original and that answer miss a step, which is to then collect that name properties from those next_evolution values.
So here is a simple function which should filter the list to find the correct items. To use it with a call to your API, I wrap it in a fetch call, and simply console.log the results. Obviously, you might well have other ways to call it.
const infoOfPokemon = (name, all) => all.filter(pokemon =>
(pokemon.next_evolution || []).map(p => p.name).includes(name)
)
fetch('https://raw.githubusercontent.com/Biuni/PokemonGO-Pokedex/master/pokedex.json')
.then(resp => resp.json())
.then(allPokemon => console.log(
infoOfPokemon('Butterfree', allPokemon.pokemon) //~> [{Caterpie}, {Metpod}]
))
You cannot use includes function directly on array having objects instead of single object. It will give false as output.
For e.g:
var pets = [{'name':'cat'},{'name':'dog'},{'name':'bat'}];
console.log(pets.includes("cat")) //false
This results in false always.
Proper way is to use a map to get a particular object field on which you want to use includes function.
e.g:
var pets = [{'name':'cat'},{'name':'dog'},{'name':'bat'}];
console.log(pets.map((obj)=> obj.name).includes("cat")); //true
In Your case first see if allPokemon[x].next_evolution is undefined or not (i.e next_evolution key is present or not)
code becomes:
if (allPokemon[x].next_evolution &&
allPokemon[x].next_evolution.(obj)=> obj.name).includes(nameOfPokemon)) { ...
I'm working on a project with search option filters and they're updated via sessions, but I'm having some issues with the session variable actually taking the array. It works fine for non-array based values, but for instance when I pass an array with RegExp objects to be used in a mongo $in selector it doesn't work as expected. The functions work fine right up until it hits Session.set() in the code snippet below so I know I have to be doing something wrong with that:
Option.prototype.update = function () {
//updates session variable if static option
if (!this.isDynamic) {
if(Object.prototype.toString.call(this.value) === '[object Array]') {
var temp = this.value.slice(0);
Session.set(this.optionName, temp);
console.log(Session.get(this.optionName));
}
else {
Session.set(this.optionName, this.value);
}
};
};
for whatever reason instead of displaying the array with values in it, it displays
[Object], and the object in that array is empty. I've read the other Overflow posts on Session variables and arrays, and simply cloning the array before passing it doesn't seem to be working. Any idea what I'm doing wrong?
Your code is correct (although slightly convoluted). The problem is that Session only takes EJSON–able values, and regexes are not EJSON–able. From the perspective of EJSON, regex looks just like an empty object, and that's exactly what you get in the stored array. Similar problem would appear if you try to store object with custom prototype, or with private (not enumerable) properties: everything that is not serialized to EJSON is lost.
The solution here is to create your own serialization method that will work with regexes. For example, if you will always have a flat array of regexes, you could simply stringify them before storing:
var temp = _.map(this.value, function(regex) {
return regex.toString();
});
I'm working with a very limited web platform which makes use of 3rd party Javascript libraries. Without listing the extraneous details of how and why it operates the way it does, I'm curious if it is possible to do something/anything (e.g. execute Javascript function) after a specific console.log entry appears. The system is very locked down but I'm trying to improve the overall user experience of the application.
A typical console log entry from this Javascript library usually looks like this:
data access_token=XXXXXXXXXXXXXXXX&type_name=user&attributes=["uuid","displayName","email"]
Googling yields a large amount of unrelated results. I found this which involves overwriting the console.log method but that's not my desired approached: How to get the console.log content as string in JavaScript
Any ideas? I'm assuming you convert the current contents into an array or string and parse for results.
You can override console.log() AND, keep it still logging to the console so you can both capture the output and leave logging in place.
Here's a way to do that:
var logEntries = [];
(function(oldLog) {
console.log = function(arg) {
// captures only first argument to console.log()
// could be expanded to concatenate all entries
logEntries.push(arg.toString());
// now call original console.log() with original arguments
return oldLog.apply(console, arguments);
};
})(console.log);
So, now at any given time, the logEntries variable will be an accumulated array of everything sent to console.log(). This is a simple version that does not expand objects or enumerate arrays. More features in that area could be added, but it appears you're just looking for a specific string.
You could also add any filtering before adding to the logEntries array if you only want to capture things containing "access_token", for example.
If you wanted to only capture the lines that contain "access_token=", then you could modify the above code like this:
var logEntries = [];
(function(oldLog) {
console.log = function(arg) {
if (typeof arg === "string" && arg.indexOf("access_token=") !== -1) {
logEntries.push(arg);
}
// now call original console.log() with original arguments
return oldLog.apply(console, arguments);
};
})(console.log);
I have a 2D array.
I currently access that array using notation such as:
myArray[5][9] (for example).
What is the safest way to check whether or not a certain array element exists?
For example, let's say I am looping through the array and retrieving a property of each array element like so:
myArray[5][9].firstName
I then come to myArray[9][11].firstName (for example) which doesn't exist. Clearly this will throw an exception as the element doesn't exist.
How can I deal with this? I'm not looping through the entire array (i'm accessing it's contents randomly and say using myArray.lengthin a for loop will not work.
Is there a JS function / method for checking whether or not an array element exists?
Thanks.
Safe call operator ?. looks fine. Warning: many, but not all implementations (and versions) of JavaScript supports it.
For your example it will looks like
myArray[5][9]?.firstName
EDIT: Thanks to Asaf's comment there is safer version
myArray?.[5]?.[9]?.firstName
like
if (!('firstname' in myArray[i][j])) { ... }
Just check it with if condition.
if(myArray[i][j].firstName){
}
You can use the hasOwnProperty method to check if an array item exists:
if (myArray.hasOwnProperty(x) && myArray[x].hasOwnProperty(y)) {
var name = myArray[x][y].firstName;
}
This checks both dimensions. If you know that the first index (x in the example) is always inside the range, you can skip the first test.
If you store some other values in the array also, you would need to check if the item has the firstName property:
if (myArray.hasOwnProperty(x) && myArray[x].hasOwnProperty(y) && myArray[x][y].hasOwnProperty('firstName')) {
var name = myArray[x][y].firstName;
}
On return of a JSON file I can't seem to be able to detect how many results are returned. The problem seems to be with the JSON file returning a diffrent number of items each time. At times it will return 1 item, then at other it will return more than 1. You see, I'm trying to get the very first result from the JSON file so I can display it. Now, If change the code everytime I know the number that will be returned, the following two bits of code work.. Artists.id; and Artists.id[0];, but I can't seem to make them work together, at the momment..
If 1 result is returned, Artists.id; will successfully bring back the artist ID;
If more than 1 result is returned Artists.id; will return "undefined".
So I need to change it to Artists.id[0]; if the JSON file returns more than 1 item. However when I change it to this, if the JSON conatins 1 item, it will return "undefined".
It seems I need some code to tell me if the returned array has 1 or more items. I've tried arr.length but that doesn't seem to be working (perhaps i miss-coded it). I also tried if(arr===undefined) and that failed to work too. The code below is what I have come up with, using the artistzero, but it is not working. Anyone has any advice? or a reason why the code below would not work?
Current Code:
$.ajax(
{
type: "GET",
url: id_url,
dataType: "jsonp",
success: function (responseData, textStatus, XMLHttpRequest)
{
if (responseData.Artists.Artist)
{
var Artists = responseData.Artists.Artist;
var artistzero = Artists.length;
if (artistzero >= 2)
{
// if more than one result is returned
var artisttype = Artists.id[0];
}
if (artistzero <= 1)
{
// if one result is returned
var artisttype = Artists.id;
}
}
else
{
$('body').append('No results');
}
}
});
Sample JSON with 1 result:
{"Artists":{"total":"1","count":"1","start":"1","errorCount":"0","Artist":{"id":"33291476","flags":"123010","catzillaID":"0","website":"","name":"Jamie T","rating":"-1","ItemInfo":{"Relevancy":{"index":"1316"}},"hotzillaID":"1809709440","url":"http://web.com/jamie-t/","trackCount":"96"}}}
Sample JSON with more than one result:
{"Artists":{"total":"1087","count":"3","start":"1","errorCount":"0","Artist":[{"id":"256212","flags":"123523","catzillaID":"1927205428","website":"http://www.bobmarley.com/","name":"Bob Marley","rating":"-1","ItemInfo":{"Relevancy":{"index":"718"}},"hotzillaID":"1802045595","url":"http://web.com/bob-marley/","trackCount":"12706"},{"id":"312874","flags":"124611","catzillaID":"1927580000","website":"http://www.bobdylan.com/","name":"Bob Dylan","rating":"-1","ItemInfo":{"Relevancy":{"index":"694"}},"hotzillaID":"1800021697","url":"http://web.com/bob-dylan/","trackCount":"4987"},{"id":"268472","flags":"41603","catzillaID":"1927193413","website":"","name":"Bob Wills","rating":"-1","ItemInfo":{"Relevancy":{"index":"644"}},"hotzillaID":"1800264434","url":"http://web.com/bob-wills/","trackCount":"2364"}]}}
You need to access the first artist before grabbing the id (since it's an array) like this:
var artisttype = Artists[0].id;
It would be better if you could change the JSON to always return an Array, even with one result...unfortunately some platforms don't do this, for reasons beyond my comprehension.
for(var propertyname in responseData){
//will loop through the different elements in your json array
alert(responseData[propertyName]); //will output the valueof each element
}
You're right that this is problematic, and to be honest it sounds like the "other end" that's sending you the JSON is being inconsistent.
The problem is that when there are multiple items they're sending you an array for the id property, and when there's a single item they're just sending you a simple value (e.g. an integer). Ideally, when there is a single item you should be sent a single-item array - this would let you use the same array-based parsing code every time.
If you can't convince them to change what they're sending you, though, then the best bet is simply to do what you're currently doing; see if Artists.id is defined, use it if so, else fall back to accessing id as an array.
However, if more than 1 result is returned Artists.id; will return "undefined". So I need to change it to this: Artists.id[0];
this cannot be Artists.id should be "object" not undefined if Artists.id[0] exists. Maybe it is as stated Artists[0].id ? and if so you could test typeof(Artists) == typeof([])