I'm using Angular and I'm trying to access property img of my object, and when I'm doing console.log(..) of my whole object. Value is there, but when I'm doing console.log(..) of object's property it said it's null.
console.log("Product:", this.article);
var url = this.article.img;
console.log("Image" , url);
Console:
I don't know how is this possible if this.article.img; looks like has some value in console.log. But when I try to access it, it says it's null. How come?
The object isn't rendered immediately. Your img property has a null value at logging time but when you open the object in the console, later, it's filled.
You can check that by logging console.log(JSON.stringify(this.article)).
The most probable reason of your problem is some asynchronous code whose achievement you're not correctly waiting for. As the object is taken from a database as you said, I guess you forget to use the object in the callback (which might be promise based).
Instead of logging:
console.log("Product:", this.article);
var url = this.article.img;
console.log("Image" , url);
try debugging, so that you can inspect the value in real time:
console.log("Product:", this.article);
debugger;
...
Because the browser console works with references in most modern clients:
Please be warned that if you log objects in the latest versions of Chrome and Firefox what you get logged on the console is a reference to the object, which is not necessarily the 'value' of the object at the moment in time you call console.log(), but it is the value of the object at the moment you click it open.
See: https://developer.mozilla.org/en-US/docs/Web/API/Console/log
Related
I am trying to read some data what I have.
My console is showing that it looks like this:
{
"calls":"0",
"ids":[
{
"id":"5117-9e39-7afd-46b3-a066-14e4-3433-871f",
"feat":{
"dates":{
"exp":"2018-10-02"
},
"read":[
{
"name":"Joe"
}
]
}
}
]
}
So I'm trying to console.log so it gives me the name.
I've done this:
console.info(data.ids.read.name)
This is returning undefined.
How can I get it to return the name?
Based on your comment showing the whole of data, you would need to use data.ids[0].feat.read[0].name to get the name.
Note that ids and read hold arrays, hence the need for the [0].
based on what you describe I think your problem is caused by you logging an object and logging a particular member of the object.
The console.log statement will give you a preview that you can expand, the preview shows the object as it is when you log it. It will sometimes give you an option to expand it and that expanded view will show the object as it is now.
When you log a primitive value or get a non expandable preview then you'll always see the object as it is when you log it.
Nikhil's suggestion to log the JSON string from the object is a good tip since you will log the object as is when you log it (string is primitive and won't give you an expand option). You could also use console.table.
Below you can see the behavior and difference of preview and expanded (you can run it in the browser's console):
var arr = [];
console.log('empty array?',arr);//previews to [] but expands to array with one object
console.log('undefined wont change',arr[0])//logs undefined because arr is still empty
arr.push({name:'ben'});//mutate array to add one item
You may be logging something that is mutated later by a resolving promise or from a callback.
I faced a problem when i console my object it shows blank but mean time when i expand the object it shows correct value, and from my controller end i cannot catch the value What's the problem?
that means.
console.log(object.limit)
-->undefined
I have faced a similar problem multiple times, majorly it's due to a
sync behavior of the variable, so at time you are checking the
variable might not have that value, sometimes it's not a JavaScript
Object, or sometimes there is a very silly mistake as .limit instead
of .limit .
Some tips for debugging
Check output of Object.keys(objectVariable).
I hate this, but try doing alert(objectVariable) as it will print the value at that time of execution, where console.log prints latest variable value regardless of when printed.
Try printing JSON.stringify(objectVariable), same as alert but in console, also prints value at time of execution not latest.
Try to define one varible in console
var object = { limit:"1",skip:'2'};
console.log(object.limit);
As per the jkondratowicz comment, Objects are passed by reference to console. When you console.log it, at that moment it's empty, only later are those two properties added.
properties are added inside object depending on JavaScript implementation.
Hence, When you are trying to do console.log(object.limit) that time your object is an empty object but after some lines of code you are adding the properties(limit) into the object and then it is available into the object.
I have a really weird issue, can someone explain please.
In my controller, when I am logging an object
console.log($rootScope.authUser)
it returns:
where messages is an array of objects. When I am trying to access one of the properties though:
console.log($rootScope.authUser.messages)
I am getting an empty array - different results! How is this possible 0.o
Try to use
console.log(angular.copy($rootScope.authUser))
It seems that console.log prints the complete object reference, and at the time you look at it, it has already changed. If you make a copy, the copy will not be changed further and you got the "real" output at that time.
I am trying to modify a property of an object.
console.log(dataset);
// -> This shows object with an 'ids' property, and it is an array with 7 elements.
But
console.log(dataset.ids); //shows an empty array
Please take a look at this image, it describles how 'dataset' look like: weired js
Can you explain why?
Thank you!
It's probably because your dataset.ids array isn't filled yet on the init.
Why?
When your open your panel from the Chrome console to inspect in details of dataset, Chrome console just recall a console log on the reference object.
At this time, the array is filled.
You should probably search a hook from your KanbanView object where you are sure this array is filled if you want to access it.
This console behavior could be confusing the first time when you face such case!
I have the following code:
var doneFile=convertToMOSTEM(curFile.file,curFile.color,curFile.importance);
console.log('doneFile:');
console.log(doneFile);
debugger;
filesOS.add(doneFile);
debugger;
convertToMOSTEM returns a custom object. The console.log logs the custom object created by convertToMOSTEM to the console, but at the debugger statement directly after the console.log logs it as a different object. I do not wish to elaborate more about the contents of convertToMOSTEM, and am instead asking for situations where this can happen. I can say, however, that convertToMOSTEM creates a custom object with a custom constructor, and then it modifies some of the properties of that custom object, then returns the modified object. The console.log logs the correct version of the object, but the object that I get in the debugger statement is like a clean version of the custom object without the extra modifications applied by the convertToMOSTEM function. I am not sure if that is very clear, if you have any questions please ask me questions in the comments.
One possibility is that you're being misled by one bit of behavior that console.log() has that isn't obvious.
When you log an object, the console doesn't save all of the properties of that object for display later. The only real-time display is whatever the single-line printout from console.log() shows. If you click the triangle to expand an object that was displayed with console.log(), the expanded display shows the properties of that object at the time you click the triangle, not at the time of the original console.log() call.
To avoid this, log the individual properties you are interested in at the time of making the call. For example, if you have a person object with id, name, and email properties, don't do this:
console.log( person );
Do this instead:
console.log( person.id, person.name, person.email );
That way, if those three properties are string values, you will log their actual values at the time you make the console.log() call.