Convert nested array to an object

Question

I am trying to use reduce to convert a nested array to an object.

I want to convert var bookprice = [["book1", "$5"], ["book2", "$2"], ["book3", "$7"]];

to

var bookpriceObj = {
    "book1": "$5", 
    "book2": "$2",
    "book3": "$7"
};

here is what I tried

var bookprice = [["book1", "$5"], ["book2", "$2"], ["book3", "$7"]];
bookpriceObj = {};
bookprice.reduce(function(a, cv, ci, arr){
    for (var i = 0; i < arr.length; ++i)
        bookpriceObj [i] = arr[i];

    return bookpriceObj ;
})

but the below result is not the desired result

{
    ["book1", "$5"]
    ["book2", "$2"]
    ["book3", "$7"]
}

Answer 1

Using forEach is shorter

var bookprice = [["book1", "$5"], ["book2", "$2"], ["book3", "$7"]];

var bookpriceObj = {};


bookprice.forEach(e=>bookpriceObj[e[0]] = e[1]);

console.log(bookpriceObj)

Answer 2

You can use reduce with Array Destructoring.

    bookpriceObj = bookprice.reduce((a, [b, c]) => (a[b] = c, a), {});

Here's what's happening:

• a is the accumulator which has an initial value of the final parameter passed to reduce. The last value we pass is {} so it's an object
• Array Destructoring can immediately assign values in an array to variables. a.e. [a, b] = ["one", "two"] assigns a with a value of "one" and b with a value of "two"
• with each iteration over each item we assign the value of b(a.e. "book1") as a property on the object(a) and give it a value equal to c(a.e. "$2")
• Each iteration of reduce you must return the accumulator(a)
• When the whole thing is finally done, it'll store in bookpriceObj the result!

var bookprice = [ ["book1", "$5"], ["book2", "$2"], ["book3", "$7"]],
bookpriceObj = bookprice.reduce((a, [b, c]) => (a[b] = c, a), {});

console.log(bookpriceObj)