`Fetch` API inside a Typescript function

Question

I am using isomorphic-fetch package inside a typescript class and trying to identify how I can return the value of the fetch api response.

somefunction(someParam: Int): Int {
  fetch('myApiURL', { method: 'get'})
    .then(function(res) {
       return res
    })
    .catch(function(ex) {
       return 0
    })
}

basarat · Accepted Answer · 2016-08-19 05:16:40Z

2

You can't return a value like Int because JavaScript is single threaded and the function cannot hold the thread hostage till it returns. However you can return a Promise, that is what fetch returns anyways so:

somefunction(someParam: number): Promise<number> {
  return fetch('myApiURL', { method: 'get'})
    .then(function(res) {
       return res
    })
    .catch(function(ex) {
       return 0
    })
}

PS: there is no int. Just number in JavaScript / TypeScript :)

answered Aug 19, 2016 at 5:16

basarat

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2 Comments

Rjk Over a year ago

thanks basarat. In that case how can I unwrap the promise and get the value.

basarat Over a year ago

Chain with a then somefunction(123).then(val=>{/*use val*/});. More basarat.gitbooks.io/typescript/content/docs/promise.html

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