Converting an array into an object

Question

I have an array of this fashion:

var arr = ["akira",9248,"padilla",100];

I'm using filter to take the names and the points:

var names = arr.filter(function(e,i){return i%2 == 0});
var points = arr.filter(function(e,i){return i%2 !== 0});

Then I do this to obtain turn it into object:

console.log(JSON.stringify(_.object(names,points)));

What's best in terms of performance/JS quality?

Answer 1

Could you do it this way which would mean you're only traversing the array once?

var obj = {};

for (var i=0; i < arr.length - 1; i = i + 2) {
    obj[arr[i]] = arr[i+1];
}         

Answer 2

I was wondering if I could do the same with reduce... and I did:

var arr = ["akira",9248,"padilla",100];

var obj = arr.reduce((carry, item, i, array) => {
  if(!(i%2)) carry[item] = array[i+1];
  return carry;
}, {});

document.write(JSON.stringify(obj));

Answer 3

My suggestion is:

var arr = ['akira', 9248, 'padilla', 100];
var obj = {};
var len = arr.length;
for (; len;) {
  obj[arr[--len]] = arr[--len];
}
alert(JSON.stringify(obj));

• A simple for is much faster than a filter.
• Iterating through an array backwards is faster than going forward.