CODEWITHSUNDEEP
javascriptnode.jsdictionaryasync-await
user16041868
user16041868

Reputation:

fetching async await data outside map function in node js / javascript

let object = [{
  id: `01`, name: `fish`, type: `marine`,
}, {
  id: `02`, name: `fish`, type: `fresh`,
}, {
  id: `03`, name: `fish`, type: `tank`,
}, {
  id: `04`, name: `animal`, type: `pet`,
}, {
  id: `05`, name: `animal`, type: `wild`,
}, {
  id: `06`, name: `animal`, type: `zoo`,
}, {
  id: `07`, name: `food`, type: `veg`,
}, {
  id: `08`, name: `food`, type: `non-veg`,
}]

let data = []
object.map((value) => {
  data.push([value.name, value.type])
})

console.log(data)

I can fetch data outside the map function in first example but in second second example i can't fetch data

let object = [{
  id: `01`, name: `fish`, type: `marine`,
}, {
  id: `02`, name: `fish`, type: `fresh`,
}, {
  id: `03`, name: `fish`, type: `tank`,
}, {
  id: `04`, name: `animal`, type: `pet`,
}, {
  id: `05`, name: `animal`, type: `wild`,
}, {
  id: `06`, name: `animal`, type: `zoo`,
}, {
  id: `07`, name: `food`, type: `veg`,
}, {
  id: `08`, name: `food`, type: `non-veg`,
}]
    
let data=[];
let test;
object.map(async (value) => {
  test = await getValue(value.name);
  data.push([value.name,value.type,test]);            
})
console.log(data);

As in first example i can easily fetch data outside the map function fut in second function I am getting blank array how can i fetch async await data outside map function

Upvotes: 2

Views: 930

Answers (4)

Aakash
Aakash

Reputation: 167

let object = [{
  id: `01`, name: `fish`, type: `marine`,
}, {
  id: `02`, name: `fish`, type: `fresh`,
}, {
  id: `03`, name: `fish`, type: `tank`,
}, {
  id: `04`, name: `animal`, type: `pet`,
}, {
  id: `05`, name: `animal`, type: `wild`,
}, {
  id: `06`, name: `animal`, type: `zoo`,
}, {
  id: `07`, name: `food`, type: `veg`,
}, {
  id: `08`, name: `food`, type: `non-veg`,
}]
    
async function demo(){
    
 let data=[];
 let test;

 for( const value of object){
   test = await getValue(value.name);
   data.push([value.name,value.type,test]);
 }

 console.log(data);
}

Try this I hope this will work as you have to write your code in for loop what you are trying to achieve it will work

Upvotes: 0

Alfred Huang
Alfred Huang

Reputation: 18265

Note that the map function yields a Promise object as a return value for each item.

And the moment when data finishes collecting all the data should come after all the Promises finishes.

So to ensure the procedure finishes, use a await Promise.all() before you use the data.

let object = [{
  id: `01`, name: `fish`, type: `marine`,
}, {
  id: `02`, name: `fish`, type: `fresh`,
}, {
  id: `03`, name: `fish`, type: `tank`,
}, {
  id: `04`, name: `animal`, type: `pet`,
}, {
  id: `05`, name: `animal`, type: `wild`,
}, {
  id: `06`, name: `animal`, type: `zoo`,
}, {
  id: `07`, name: `food`, type: `veg`,
}, {
  id: `08`, name: `food`, type: `non-veg`,
}]

let data=[];
let test;
let promises = object.map(async (value) => {
  test = await getValue(value.name);
  data.push([value.name,value.type,test]);            
})

// 1. This line matters
await Promise.all(promises);
console.log(data);

// 2. Or if you cannot use await here
Promise.all(promises).then(() => {
  console.log(data);
});

By the way, because the getValue function is asyncronous, so you possibly will got the data in a completely random order, if you care about the order, you may need another approach.

Upvotes: 2

Rajesh Verma
Rajesh Verma

Reputation: 307

Try this you will get your response viva for loop easily. Map function uses a callback function which to be traversed on each element for given array. For more details just go throug this async/await for Array.map fuction, can also use the promise.all for the same as mentioned in post in the given link.

let object=
    [
     {
      id:`01`,
      name:`fish`,
      type:`marine`,
     },
     {
      id:`02`,
      name:`fish`,
      type:`fresh`,
     },
     {
      id:`03`,
      name:`fish`,
      type:`tank`,
     },
     {
      id:`04`,
      name:`animal`,
      type:`pet`,
     },
     {
      id:`05`,
      name:`animal`,
      type:`wild`,
     },
     {
      id:`06`,
      name:`animal`,
      type:`zoo`,
     },
     {
      id:`07`,
      name:`food`,
      type:`veg`,
     },
     {
      id:`08`,
      name:`food`,
      type:`non-veg`,
     }
    ]

    const getData = async function(){
      let data=[];
      for (var i=0; i<object.length; i++){
        let value = object[i];
        let test= await getValue(value.name);
        data.push([value.name,value.type,test]);  
      }
      return data;
    }

console.log(await getData());

Upvotes: 1

Cully
Cully

Reputation: 6975

Use Promise.all:

const data = await Promise.all(object.map(async (value) => {
  const test = await getValue(value.name);
  return [value.name,value.type,test]
}))

console.log(data)

Upvotes: 1

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