how to access elements in javascript array

Question

how do I access the integers in the data object of this array?

Ultimately, I want to write a for loop to enter and compute the vpos (vertices).

var arrays = {
vpos : { numComponents: 3, data: 
                [
                    -.5,-1,-.5,  .5,-.5,-.5,  .5, .5,-.5,
                    -.5,-.5,-.5,  .5, .5,-.5, -.5, .5,-.5,
                    -.5,-.5, .5,  .5,-.5, .5,  .5, .5, .5
                ] },
    vnormal : {numComponents:3, data: [
                    0,0,-1, 0,0,-1, 0,0,-1,
                    0,0,-1, 0,0,-1, 0,0,-1,
                    0,0,1, 0,0,1, 0,0,1,
                    ]}
            };

What are you trying to compute the sum of the vpos? – Get Off My Lawn Nov 30 '17 at 23:39 — Get Off My Lawn, Nov 30 '17 at 23:39

score 1 · Accepted Answer · answered Nov 30 '17 at 23:43

You can easily calculate the total with reduce:

let total = arrays.vpos.data.reduce((sum, val) => sum + val, 0);

Here is a demonstration:

var arrays = {
  vpos: {
    numComponents: 3,
    data: [-.5, -1, -.5, .5, -.5, -.5, .5, .5, -.5, -.5, -.5, -.5, .5, .5, -.5, -.5, .5, -.5, -.5, -.5, .5, .5, -.5, .5, .5, .5, .5]
  }
};

let total = arrays.vpos.data.reduce((sum, val) => sum + val, 0);
console.log(total);

score 0 · Answer 2 · answered Nov 30 '17 at 23:40

0

Just use [index] notation. Index is zero-based (first item has index of 0, 2nd one - 1, and so on).

arrays.vpos.data[0] //gives -0.5
arrays.vpos.data[1] //gives -1
arrays.vpos.data[2] //gives -0.5

answered Nov 30 '17 at 23:40

entio

3,816
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39

score 0 · Answer 3 · answered Nov 30 '17 at 23:41

0

For vpos:

var pushedArray;
for(var x of arrays.vpos.data) {
    pushedArray.push(x);
}

pushedArray will have the values from the data array in it.

To add them:

var sum;
for(var x of pushedArray) {
    sum += x;
}

answered Nov 30 '17 at 23:41

ewizard

2,801
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110

score -1 · Answer 4 · answered Nov 30 '17 at 23:42

Yes you can get data array in d and then create for loop

var v =  {
vpos : { numComponents: 3, data: 
                [
                    -.5,-1,-.5,  .5,-.5,-.5,  .5, .5,-.5,
                    -.5,-.5,-.5,  .5, .5,-.5, -.5, .5,-.5,
                    -.5,-.5, .5,  .5,-.5, .5,  .5, .5, .5
                ] },
    vnormal : {numComponents:3, data: [
                    0,0,-1, 0,0,-1, 0,0,-1,
                    0,0,-1, 0,0,-1, 0,0,-1,
                    0,0,1, 0,0,1, 0,0,1,
                    ]}
            };
            var d = v.vpos.data;
            console.log(d);

how to access elements in javascript array

4 Answers4