Filtering objects in JavaScript using a technique similar to list comprehension

Question

I'm dealing with a basic array structure that resembles:

obj = {1:false, 2:true, 3:true}

My goal is to extract an array containing all the keys in the object that have a value of true.

In Python, you can achieve this easily using:

>>> [key for key in obj if obj[key]]
[2, 3]

Is there a succinct or one-line method to accomplish this task in JavaScript? I also happen to have lodash at my disposal.

Answer 1

Answer №1

For those with Ecma5 compatible browsers, you have the ability to achieve this by utilizing Object.keys and Array.filter:

> Object.keys(data).filter(function(key) {return data[key]});
> ["4", "5"]

Answer 2

For those with Ecma5 compatible browsers, you have the ability to achieve this by utilizing Object.keys and Array.filter:

> Object.keys(data).filter(function(key) {return data[key]});
> ["4", "5"]

Answer 3

To achieve this using the latest JavaScript syntax, follow these steps:

const obj = {A:false, B:true, C:true};

const result = Object.keys(obj).filter(key => obj[key]);

console.log(result);

Answer 4

To achieve this using the latest JavaScript syntax, follow these steps:

const obj = {A:false, B:true, C:true};

const result = Object.keys(obj).filter(key => obj[key]);

console.log(result);

Answer 5

If you're using Firefox version 30 or higher, you can achieve this.

obj = {1:false, 2:true, 3:true};
[for (key of Object.keys(obj)) if (obj[key]) key ];

This code snippet will give the following output:

["2", "3"]

As of now, Firefox is the sole browser that supports Array Comprehension.

Answer 6

If you're using Firefox version 30 or higher, you can achieve this.

obj = {1:false, 2:true, 3:true};
[for (key of Object.keys(obj)) if (obj[key]) key ];

This code snippet will give the following output:

["2", "3"]

As of now, Firefox is the sole browser that supports Array Comprehension.