I want to create an rxjs Observable that runs a long polling operation. Each iteration emits intermediate results. When isComplete returns true, the Observable completes. This function should behave as follows It should start only when there’s at least one subscriber It should allow multiple subscribers to share the results It should abort the polling and call cancel if there
Tag: typescript
Javascript cannot change the value of mydata
I have this code: And after I try to add some values: I keep getting: How can I fix this? Answer You can’t set a property on null. You need to assign an object to your variable first: Or all in one go:
filter value of select to do a partial sum
Having two classes professor and student: professor.ts student.ts To add up the scores of each student relative to his teacher I did: This is the HTML of the page: How can I do a partial sum of the selections, assuming for example that I have 5 professor with 1 student for every professor, and want to add only the results
Why won’t setMatrix([…matrix, [[x][y]]]) work?
I want to add the coordinates x and y (from the loop) to the state (matrix) like you can see in my example but it won’t work. Can someone help me? Answer The problem is in expression [x][y] which evaluates to undefined. [x] defines an array containing one element x [x][y] tries to index the [x] array, taking y-th element.
React + TS – pass parameters with redirect
Hello i have application where i want to redirect user after successfully create a new room. I want to redirect him to page with room ID in URL, but i want to send data with this redirect to the component state. in App.tsx i have im redirect from CreateRoom component like this that works fine and redirect me. this is
How to use `(K | V)[][]` as `ReadonlyArray` in a Map?
I would like to use a (K | V)[][] as ReadonlyArray<[K, V]> in a Map constructor. Lets say that our V is an interface IItem and K a basic number. By default, typescript will perceive the type of items as : (number | IItem)[][]. This will not work and throw an error: Argument of type ‘(number | { key: number;
myComponent.map is not a function
I have this information right now that i’m saving and trying to pass to a component who then tries to create Tabs and TabPanel (Material-ui components) with said info. The declaration of that info goes as follow : I then proceed to pass said info to my component: On the other side i have an interface that contains the same
How to filter data on Object in Angular
I get data from backend with this function and console.log(response) show JSON like below What I want are data that have “is_family_member”: false, for this I create this.personmembertrue = this.persons.filter(x => x.is_family_member === ‘false’) this part of code show empty. Any idea please how to show data with “is_family_member”: false Answer Change the condition to: See if that works.
How to conditionally add a key to an object?
Consider these types: I want to convert an object of type A into B by overwriting some keys and adding keys conditionally depending on whether the original object has them: TypeScript throws this error: Why is it inferring b in this way? Is there a way to work around it? Answer It’s a combination of two minor design limitations and
How filter and sort in a nested tree Array in javascript?
I need to filter and sort a nested tree object for menu so is sort and filter status === true ,How to turn to Answer I would write two recursive functions: One to filter out the status: false items One to sort items by their sort property You can combine the two in any order you like. itemFilter The filter