Question

I have the following big array:

var divs = [
    {class:'A', top:0,   left:0},
    {class:'B', top:50,  left:60},
    {class:'C', top:30,  left:10},
    {class:'D', top:100, left:180},
    {class:'E', top:80,  left:50},
    {class:'F', top:100, left:200},
    {class:'G', top:50,  left:80}
];

I’d like to isolate just the top values. I tried using split() but I might not be using it correctly because nothing returns as expected.

Once the top values are isolated into their own smaller array I want to iterate over it and find the frequency of occurrence for each value.

Can I please get some help?

Answer 1

var divs = [
            {class:'A', top:0,   left:0},
            {class:'B', top:50,  left:60},
            {class:'C', top:30,  left:10},
            {class:'D', top:100, left:180},
            {class:'E', top:80,  left:50},
            {class:'F', top:100,  left:200},
            {class:'G', top:50,  left:80}
];
var topsy = {};
for(var i = 0, max = divs.length; i < max; i++){
    var a = divs[i];
    topsy[a.top] = (topsy[a.top] + 1) || 1;
}

At this point, you will have a topsy that has all of the tops in there, with the key being the top, and the value being the number of times it was in there. To get a list of the keys, you say:

Object.keys(topsy);

Object.keys doesn’t work in IE.
You will end up with topsy =

{
    0: 1,
    30: 1,
    50: 2,
    80: 1,
    100: 2
}

Then you can say

Object.keys(topsy);//[3,30,50,80,100]

You got your analysis and array done at one time.