Reusing promises
I am trying to call getPromise function with different urls to return different promises, but getting undefined in the second promise then success function.
var http=require('http');
var URL='http://localhost:3000';
var getPromise=function(url){
var promise=new Promise(function(resolve,reject){
http.get(url,function(response){
if(response.statusCode < 200 || response.statusCode > 299){
reject(new Error('ErrorCode '+response.statusCode))
}
var result="";
response.on('data',function(chunk){result +=chunk;} )
response.on('end',function(){resolve(result);} )
})
});
return promise;
}
getPromise(URL+'/olympic/2016/ranking/4')
.then(function(data){
console.log("Response "+JSON.parse(data).Country);
getPromise(URL+'/iso/country/'+JSON.parse(data).Country);
})
.then(function(data){
console.log("Data "+data)
})
.catch(function(err){
console.log(err)
});
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4 answers
Make sure you return the data from the promise then
:
getPromise(URL+'/olympic/2016/ranking/4')
.then(function(data){
console.log("Response "+JSON.parse(data).Country);
return getPromise(URL+'/iso/country/'+JSON.parse(data).Country);
})
.then(function(data){
console.log("Data "+data)
})
.catch(function(err){
console.log(err)
});
Whatever you return from the callback then
will be passed down the promise chain. You are not returning anything right now, so you are implicitly returning undefined
.
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You need to return data for the next "then" to get it.
getPromise(URL+'/olympic/2016/ranking/4')
.then(function(data){
console.log("Response "+JSON.parse(data).Country);
return getPromise(URL+'/iso/country/'+JSON.parse(data).Country);
})
.then(function(data){
console.log("Data "+data)
})
.catch(function(err){
console.log(err)
});
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You can change the function
getPromise(URL+'/olympic/2016/ranking/4')
.then(function(data){
console.log("Response "+JSON.parse(data).Country);
getPromise(URL+'/iso/country/'+JSON.parse(data).Country)
.then(function(data){
console.log("Data "+data)
});
})
.catch(function(err){
console.log(err)
});
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You are missing return
:
getPromise(URL+'/olympic/2016/ranking/4')
.then(function(data){
console.log("Response "+JSON.parse(data).Country);
/////////// here
return getPromise(URL+'/iso/country/'+JSON.parse(data).Country);
})
.then(function(data){
console.log("Data "+data)
})
.catch(function(err){
console.log(err)
});
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