Nested Async ForEach loops

Question

I have a two nested forEach loops, i tried using standard forEach and some own logic but it failed, than i tried the async library from npm with the code bellow:

function addValue(data, callback){
    var final_data = [];
    data.forEach(element => {
        final_data.push(element);
    });
    var values = 
    [[1,0],
    [2,0],
    [3,0],
    [-1,0],
    [-2,0],
    [-3,0],
    [1,1],
    [2,1],
    [3,1],
    [-1,1],
    [-2,1],
    [-3,1]];
    async_.forEachOf(final_data, (item, {}, callback1) => {
        values.forEach(value=>{
            var obj = Object.assign({},item);
                    obj.x+=value[0];
                    obj.y+=value[1];
                    final_data.push(obj);
        });
        callback1();
    }, err => {
        if (err) console.error(err.message);
        // Here i get different values for separate executions with same data
        console.log(final_data.length)
    });
}

What i am trying to achieve is that final_data is an array of objects, the first forEachOf loop should iterate through the final_data object and for each of them should run the second nested forEach creating a new object with modified values and pushing it back in the final_data array of object. The problem i am encountering is that the function always returns at a different time, hence the lenght of the final_data is always different, once 100 objects get pushed, once 670. So basically the callback in the main function which is addValue should be called once all of the objects are processed and the two for loops finish...

Using non-async code end up in infinite loop, strange

function addValue(data, callback){
    var final_data = [];
    data.forEach(element => {
        final_data.push(element);
    });
    var values = 
    [[1,0],
    [2,0],
    [3,0],
    [-1,0],
    [-2,0],
    [-3,0],
    [1,1],
    [2,1],
    [3,1],
    [-1,1],
    [-2,1],
    [-3,1]];
    for(var i=0; i<final_data.length; i++){
        for(var j=0; j<values.length; j++){
            var obj = Object.assign({},final_data[i]);
            obj.x+=values[j][0];
            obj.y+=values[j][1];
            final_data.push(obj);
            console.log(final_data.length)
        }
    }
}

EDIT 2: Using forEach with no async works... What might be the cause of the infinite standard loop, versus the forEach ?

There doesn't seem to be any async code here, so is there any reason your trying to do async coding.? — Keith
– Keith, Commented Apr 23, 2019 at 9:27
Do you want to call the callback with new obj and get the result?Is that what you need? — Shyam Babu
– Shyam Babu, Commented Apr 23, 2019 at 9:38

Shyam Babu · Accepted Answer · 2019-04-23 10:17:13Z

1

You can try this assuming you have es6 support

function addValue (data) {
 var values = 
[[1,0],
[2,0],
[3,0],
[-1,0],
[-2,0],
[-3,0],
[1,1],
[2,1],
[3,1],
[-1,1],
[-2,1],
[-3,1]];
var finalData = data.map((item)=>{
   return values.map(function(value) {
        var obj = Object.assign({},item);
                obj.x+=value[0];
                obj.y+=value[1];
        return obj;         
   })  
});
return finalData.flat(2);
}

answered Apr 23, 2019 at 10:17

Shyam Babu

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Comments

nivendha · Accepted Answer · 2019-04-23 10:15:06Z

0

async function addValue(data, callback){
var final_data = [];
data.forEach(element => {
    final_data.push(element);
});
var values = 
[[1,0],
[2,0],
[3,0],
[-1,0],
[-2,0],
[-3,0],
[1,1],
[2,1],
[3,1],
[-1,1],
[-2,1],
[-3,1]];
var result =[]
for(item of final_data)
   for (const value of values) {
     var obj = Object.assign({},item);
                obj.x+=value[0];
                obj.y+=value[1];
          await result.push(obj);
   }

edited Apr 23, 2019 at 10:15

answered Apr 23, 2019 at 9:21

nivendha

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6 Comments

Kristijan Stefanoski Over a year ago

In order to use await for callback1, i have to use async inside the forEachOf too right? Since otherwise it will throw error that await is valid only in async functions even though the higher scope function is async

Kristijan Stefanoski Over a year ago

@nivendha The purpose of the code is for each element of the final_data array to create N number of different copies of it and push it back to the main final_data array and return it to where ever the function addValue() is called...

Keith Over a year ago

@KristijanStefanoski So what is is you think requires any of this to use promises.? Just return final_data;, you don't even need to use a callback..

nivendha Over a year ago

@KristijanStefanoski this doesnt need an async at all i think

Kristijan Stefanoski Over a year ago

Okay, so i used non-async and i end up in an infinite loop for some reason, you can check update above.

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