Javascript - Create array dynamically in object and push to it

Question

How do I populate filters.

let filters = {};

To make it look like this:

filters = {
  color: ["Blue", "Black"],
  size: [70, 50]
};

So if I would have a function:

function populate(key, value) {
    //if key is color value gets pushed to filters.color
    //if key is size value gets pushed to filters.size
    //if any other key, create new property with new name
}

So doing this would result in a new array in filters:

populate(material, "plastic");

And filters would look like this:

filters = {
  color: ["Blue", "Black"],
  size: [70, 50],
  material: ["plastic"]
};

Hassan Imam · Accepted Answer · 2018-05-21 12:06:57Z

3

You can use in to check if the key exists in the object. Based on that push the value in the object array otherwise creates a new key with array value.

let filters = {};
filters = {
  color: ["Blue", "Black"],
  size: [70, 50]
};

function populate(key, value) {
    //if key is color value gets pushed to filters.color
    //if key is size value gets pushed to filters.size
    //if any other key, create new property with new name
    if(key in filters)
      filters[key].push(value);
    else
      filters[key] = [value];
}
populate('material', "plastic");
console.log(filters);

answered May 21, 2018 at 12:06

Hassan Imam

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Comments

Narendra Jadhav · Accepted Answer · 2018-05-21 12:08:54Z

1

You can use concat method of array if key present in filters Object otherwise it you will assign new array with new value.

DEMO

var filters = {
  color: ["Blue", "Black"],
  size: [70, 50]
};

function populate(key, value) {
  filters[key] = (filters[key]||[]).concat(value); 
}

populate('material', "plastic");
populate('color', "Red");
populate('size',55);
console.log(filters)

 .as-console-wrapper {max-height: 100% !important;top: 0;}

answered May 21, 2018 at 12:08

Narendra Jadhav

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Comments

Asons · Accepted Answer · 2018-05-21 12:33:51Z

1

You could do something simple as this, where you check if the key exist and then push or assign.

array[key] ? array[key].push(value) : array[key] = [value];

Do note, you need to pass the key "material" as a string, and I as well recommend to pass the array too, to make the function more reusable.

filters = {
  color: ["Blue", "Black"],
  size: [70, 50]
};

function populate(a, k, v) {
  a[k] ? a[k].push(v) : a[k] = [v];
}

populate(filters, "material", "plastic");

console.log(filters)

edited May 21, 2018 at 12:33

answered May 21, 2018 at 12:05

Asons

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8 Comments

Ciprian Over a year ago

won't that replace filters[key] with a new value every time the value will be material? I need to keep pushing new values to color, size or material

Asons Over a year ago

@Ciprian Updated again...somewhat more optimized, and reuseable

Andrew Bone Over a year ago

If you want to compress it a turnary might be good a[k] = a[k] ? a[k].push(v) : [v];

Asons Over a year ago

@AndrewBone That won't work... this one though a[k] ? a[k].push(v) : a[k] = [v];, so thanks

Asons Over a year ago

@AndrewBone Try it by calling populate 2 times and you'll see. After second populate the value is 2, not e.g. "plastic", "paper"

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