CODEWITHSUNDEEP
javascriptjqueryperformance
NublicPablo
NublicPablo

Reputation: 1039

Iterate through pairs of properties

Given a JS object like:

var obj = {
    p1: "v1",
    p2: "v2",
    ...,
    pn: "vn"
}

What I would like to do is to obtain an iterator over all distinct pairs of properties (both names or values would work for me).

So I could have a function like:

function(va, vb) {
    // do something with every pair
}

called once with each entry of the set of pairs ("v1", "v2"), ("v1", "v3"), ... , ("v1", "vn"), ("v2", "v3"), ... , ("v2", "vn"), ... , ("vn-1", "vn"). (A total of n(n - 1)/2 times)

The trivial solution is to have a double for ... in loop and discard the repetitions inside, but that's not either fast or elegant.

If it was an array and not an object we could have a different kind of iteration, like:

var len = obj.length;
for (var i = 0; i < len - 1; i++) {
    for (var j = i + 1; j < len; j++) {
        // do something with obj[i], obj[j]
    }
}

But I don't know any way to iterate an object like that (or if it would even make sense!).

Then, is there any fast and elegant way of doing this in javascript (or jQuery)?

Edit:

I don't want to get an iterator of (key, value) as suggested in some answers. I want an iterator over pairs of properties in an object.

I would like, for example, to run a check that verifies that every value is, at most, 10 units away from any other value.

function checkIsClose(v1, v2) {
    return ((v1 - v2) < 10 && (v1 - v2) >= 0)) || ((v2 - v1) < 10 && (v2 - v1) >= 0);
}

Upvotes: 2

Views: 114

Answers (3)

XiozZe
XiozZe

Reputation: 472

I can't think of an other way to iterate through an object like that without for ... in. But you can delete one key every time, that would make it a total of n(n - 1)/2 times.

http://jsfiddle.net/XiozZe/YTVAL/

var obj = {
    p1: "v1",
    p2: "v2",
    p3: "v3",
    p4: "v4",
    p5: "v5",
    p6: "v6",
}

//duplicate obj
var obj2 = {}
for (var i in obj) {
    obj2[i] = obj[i];
}

for(var i in obj2){
    for(var j in obj2){
        // do something with obj[i], obj[j]
    }
    delete obj2[i];
}

//obj2 is now empty

Upvotes: 2

dhana
dhana

Reputation: 6525

Try this, Demo

var obj = {
    p1: "v1",
    p2: "v2",
    pn: "vn"
}

$.each(obj, function(a, b){alert(a);alert(b)});

Update:

$.each(obj, function(a, b1){

  $.each(obj, function(a, b2){
    console.log(b1 +" ,"+ b2);
  })

});

Demo

OutPut:

("v1", "v2"), ("v1", "v3"), ... , ("v1", "vn"), ("v2", "v3"), ... , ("v2", "vn"), ... , ("vn-1", "vn"). (A total of n(n - 1)/2 times)

https://api.jquery.com/jQuery.each/

Upvotes: 3

mayrs
mayrs

Reputation: 2377

Go for jQuery.map() like so:

jQuery.map(obj, function(vb, va) {
    // do something with every pair
});

Test it in the fiddle

Upvotes: 0

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