When using Deno 0.42.0, I find it difficult to do any type of analysis of objects by using typeof or other inspection techniques I use in JavaScript.
For example:
const form = new FormData();
console.log(`typeof: ${ typeof form }`);
.. just returns object
Similarly, inspecting properties like:
const form = new FormData();
console.log(`props: ${ Object.getOwnPropertyNames(form) }`);
... returns nothing.
At least instanceof does work:
const form = new FormData();
console.log(`props: ${ form instanceof FormData }`);
... returns true
Is there a way in Deno to inspect objects in real time without first knowing what the object type is?
It works exactly like that on the browser too.
typeof possible return values are:
undefined
object
boolean
number
bigint
string
symbol
function
So it's not possible for you to get another value.
Maybe what you want is .constructor.name
const form = new FormData();
console.log(`class: ${form.constructor.name}`); // FormData
console.log(`props: ${ form instanceof FormData }`); // true
Related
I need to return an array of labels, but I can only return 1 of the labels so far. The error which I get is "Cannot set headers after they are sent to the client". So I tried res.write and placed res.end after my for loop then I get the obvious error of doing a res.end before a res.write. How do I solve this?
for(let i=0;i<arr.length;i++){
request.get(arr[i], function (error, response, body) {
if (!error && response.statusCode == 200) {
myfunction();
async function myfunction(){
const Labels = await Somefunctioncallwhoseresponseigetlater(body)
res.send(Labels);
}
}
});}
New code-
async function getDataSendResponse(res) {
let allLabels = [];
for (let url of arr) {
let body = await got(url).buffer();
var imgbuff= Buffer.from(body,'base64')
const imageLabels = await rekognition.detectLabels(imgbuff);
allLabels.push(...imageLabels);
}
res.send(allLabels);
}
The error I have with this code is
"Resolver: AsyncResolver
TypeError: Cannot destructure property Resolver of 'undefined' or 'null'."
You are trying to call res.send() inside a for loop. That means you'll be trying to call it more than once. You can't do that. You get to send one response for any given http request and res.send() sends an entire response. So, when you try to call it again inside the loop, you can the warning you see.
If what you're trying to do is to send an array of labels, then you need to accumulate the array of labels first and then make one call to res.send() to send the final array.
You don't show the whole calling context here, but making the following assumptions:
Somefunctioncallwhoseresponseigetlater() returns a promise that resolves when it is done
You want to accumulate all the labels you collected in your loop
Your Labels variable is an array
Your http request returns a text response. If it returns something else like JSON, then .text() would need to be changed to .json().
then you can do it like this:
const got = require('got');
async function getDataSendResponse(res) {
let allLabels = [];
for (let url of arr) {
let body = await got(url).buffer();
const labels = await Somefunctioncallwhoseresponseigetlater(body);
allLabels.push(...labels);
}
res.send(allLabels);
}
Note, I'm using the got() library instead of the deprecated request() library both because request() is not deprecated and because this type of code is way easier when you have an http library that supports promises (like got() does).
Is there a function to convert objects that have be converted into vuejs's reactive system back into a normal object?
I think you can try:
const normalObject = JSON.parse(JSON.stringify(objectWithReactivity)).
Even try a copy using ecmascript
object_reactive
let object = {...object_reactive}
or maybe just javascript
var obj = { a: 1 };
var copy = Object.assign({}, obj);
I was learning mongoose, and I am trying to figure out.
Why toObject() was needed to convert the data received into Object, when it was already in object form it seems
Here is the code:
UserSchema.methods.toJSON = function() {
var user = this;
var userObject = user.toObject();
return _.pick(userObject, ['_id', 'email']);
};
I cannot understand why toObject() was used to extract the meaningful properties from the object.
Thanks
toObject is a mongoose document method Document.prototype.toObject() which:
Converts this document into a plain javascript object, ready for storage in MongoDB.
You can more about it here
The reason it is called there is because a plain JS object is required in order to do the lodash _.pick which would create a new object with only _id and email properties.
I'm trying to update an array every time my tag receives an update from parent tags. Here is my code:
var tag = function(opts){
this.set = [];
var self = this;
this.on('updated', function(){
var obj = opts.my_topics;
var better_obj = {};
for (var key in obj) {
if (obj.hasOwnProperty(key)) {
var topic_title = key;
better_obj = obj[key];
better_obj['title'] = key;
}
}
self.set.push(better_obj);
})
}
Whenever I try to push(), I get an error: Uncaught SyntaxError: Unexpected token ; database.js:60. The moment I remove the line of code for the push, the error disappears. Am I using this/self wrong in this case or could it be something else?
What I am trying to accomplish here is taking an object from opts (which receives regular updates), converting into an array, and using it for an each loop within my tag. I do not know how to do this other than a) what i'm trying to do now by accessing this, or b) rewiring my opts to deliver an array rather than an object (which is currently failing for me as I'm using Redux and it doesn't like dispatching non-objects).
I am trying to add new row in datatables, and by using the API .any() to check if the id is already exist in the rows and if it exist I will not add new row to my datatable, and here is the result form my request from databse see http://pastie.org/10196001 , but I am having trouble in checking.
socket.on('displayupdate',function(data){
var dataarray = JSON.parse(data);
dataarray.forEach(function(d){
if ( table.row.DT_RowId(d.DT_RowId).any() ) { // TypeError: table.row.DT_RowId is not a function
console.log('already exist cannot be added');
}else{
table.row.add(d).draw();
}
});
});
Thank you in advance.
You get the error, of course, because DT_RowId not is a function in the API. But DT_RowId is in fact the one and only property that get some special treatment from dataTables :
By assigning the ID you want to apply to each row using the property
DT_RowId of the data source object for each row, DataTables will
automatically add it for you.
So why not check rows() for that automatically injected id along with any()?
socket.on('displayupdate',function(data){
var DT_RowId,
dataarray = JSON.parse(data);
dataarray.forEach(function(d){
DT_RowId = d.DT_RowId;
if (table.rows('[id='+DT_RowId+']').any()) {
console.log('already exist cannot be added');
} else {
table.row.add(d).draw();
}
});
});
simplified demo -> http://jsfiddle.net/f1yyuz1c/