Looping a javascript promise to append to an array

Question

Good day, below I have

    var request = require('request');
    getFood = function(lst){
        return new Promise(function(resolve, reject){
            //console.log(lst)
            request('https://api.jamesoff.net/recipe', function (error, response, recipe) {
                lst.push(JSON.parse(recipe))
                resolve(lst);
            })
        });
    }   


    getFood([]).then(function(data){
        for(var i = 0; i < 3; i++){
            getFood(data)
        }
        return(data);
    }).then(function(data){
        console.log(data)
    })

What I am aiming to accomplish is by using a promise chain place three recipies into an array using a loop. I only get one item and I know why this occurs, however I can't wrap my head around the procedure to accomplish my goal. Could I please get an explanation with code?

BShaps · Accepted Answer · 2018-03-28 23:24:40Z

5

The problem is your getFood call in a loop. If you are looping through promises the best way to do it is with Promise.all()

An example:

var promiseArray = [];
for(var i = 0; i < 3; i++){
    promiseArray.push(getFood(data))
}
Promise.all(promiseArray).then(function(values) {
    // values is array of resolve values in the order that promises were pushed into the array
});

This resolves the promises in the order in which they were called and should help with your issues.

answered Mar 28, 2018 at 23:24

BShaps

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2 Comments

hope1234 Over a year ago

Ok so the key was placing the promises into an array first then running them at the same time.. with promise.all() which I didn't know about.. Thanks!

BShaps Over a year ago

No problem. A general rule of thumb that I've found is that if you are using promises in a loop, you need to use Promise.all()

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