How to convert an array of arrays to an Object?

Question

What's the best way to convert a list of tuples to a dictionary in javascript?

One way is this:

var data = [['a',1], ['b',2],['c',3]]
var group_to_lengths = {} 

data.forEach(function(d) {
    group_to_lengths[d[0]] = d[1]; 
});

Is there a simpler or more idiomatic way of accomplishing the same thing? Perhaps like in python (group_to_lengths = dict(data))?

The concept dictionary in JS does not exist. In JS there is objects and arrays. — KiaMorot
– KiaMorot, Commented Feb 3, 2015 at 14:15

thefourtheye · Accepted Answer · 2015-02-03 14:20:58Z

4

I would recommend using Array.prototype.reduce, which is more idiomatic for this case, like this

console.log(data.reduce(function(result, currentItem) {
    result[currentItem[0]] = currentItem[1];
    return result;
}, {}));
# { a: 1, b: 2, c: 3 }

But, if you use a functional programming library, like underscore.js, then it would be just a one-liner with _.object, like this

console.log(_.object(data));
# { a: 1, b: 2, c: 3 }

answered Feb 3, 2015 at 14:20

thefourtheye

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