I want to create an array containing objects that have a key data which is an array of values. I am trying to push values into data but it's not working for me.
My expected result looks like this:
array = [
{ data:[3,2,5] },
{ data:[5,2,1] }
]
So I want to fill the data arrays. To do this, I have tried populating the arrays with a for loop:
var array = [];
for(i=0;i<2;i++){
for(j=0;j<3;j++){
array[i]["data"][j].push(2);
}
}
But this is not working for me.
You can't do this: array[i]["data"][j].push(2) without first initializing array[i].
In your case there's no need to initialize it with an empty array, instead you can simply assign the whole object to each [i]
What you are trying to achieve is an array of objects where each object is of the form {'data': []}
So assume you have your input coming from an array:
const initialData = [[3, 2, 5], [5, 2, 1]];
To get that data in the form you want it, you would do:
const initialData = [[3, 2, 5], [5, 2, 1]];
var array = [];
for(i=0;i < initialData.length; i++){
array[i] = {'data':initialData[i]};
}
console.log(array)And here is a neater approach using some of Array.prototype's methods which I recommend checking out:
const initialData = [[3, 2, 5], [5, 2, 1]];
const array = initialData.map(elem => {
return {
'data': elem
};
})
console.log(array)And if you want neaterer you can go with mplungjan's comment
const array = initialData.map(elem => ({ 'data': elem }));
You can initialize the array with: const array = [...Array(2)].map(() => ({ data: [] }));
Then you'll be able to access it with:
for(i=0; i<2; i++){
for(j=0;j<3;j++){
array[i].data[j] = 2;
}
}
Take a look at these changes, which modify your existing code. For an improved method, see the bottom
var array = [];
for(i=0;i<2;i++){
array.push({data:[]}) // create your object
for(j=0;j<3;j++){
array[i]["data"].push(2); // you don't need '[j]' because the result of 'data' key is an array, so just push onto it
}
}
console.log(array)let arr = [...new Array(2)].map(el=>({ data: new Array(3).fill(2) }));
console.log(arr)You could do something like this:
let items = 2
let arr = Array.from({ length: items }, (item) => item = { data: [] })
for (let i = 0; i < items; i++) {
for (let j = 0; j < 3; j++) {
let val = 2 // replace value here
arr[i].data.push(val)
}
}
console.log(arr);
pushis not a value method.