How Do I Use Xmlhttprequest in Typescript?
This Is a New Situation for Me, I Have Been Using Typescript for a Long Time but Struggling with Xmlhttprequest. Request. Open('Get', Path); Request. Onload =...
This is a new situation for me, I have been using TypeScript for a long time but struggling with XMLHttpRequest.
request.open('GET', path);
request.onload = () => {
// this is fine
}
request.onerror = (e: ErrorEvent) => {
// i can't figure this out
this.registerError(e);
}
How do I correctly deal with that error response? My code above fails during compilation with this:
error TS2322: Type (e: ErrorEvent) => void is not assignable to type (this: XMLHttpRequest, ev: ProgressEvent) => any
I wasn't expecting that.
If you change the code to
request.onerror = (this: XMLHttpRequest, ev: ProgressEvent) => {
};
It isn't valid typescript. Even if it was, this as a parameter name is incredibly confusing.
Would it be possible to provide an example of how to catch an XMLHttpRequest error?
1 Answer
The reason you can't specify this is because you are using an arrow function =>. You just need to change the type of the parameter:
request.onerror = (e: ProgressEvent) => {
}
You don't really need to specify the type at all as it is inferred based on the type of onerror
request.onerror = (e) => {
e // is ProgressEvent
}
If you use a regular function you can specify this
request.onerror = function(this: XMLHttpRequest, e: ProgressEvent) {
this // is XMLHttpRequest
}
Although you don't really need to as it will be implicitly typed based on the type of onerror
request.onerror = function(e: ProgressEvent) {
this // is still XMLHttpRequest
}
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