I have a list of objects:
[Object { name="abc", id=12, addr="random addr 0"}, Object { name="def", id=76, addr="random addr 1"}]
What I want:
Key value pairs of name -> id
Object { abc=12, def=76}
What I have have:
for (var i in list){
res[list[i].name]=list[i].id;
}
My question:
Is there a better way to do this?
For most index operations on arrays there are better alternatives (e.g. expressions with map(), reduce(), etc.). In this case, I would suggest reduce():
var s = [{ name:"abc", id:12, addr:"random addr 0"},
{ name:"def", id:76, addr:"random addr 1"}];
s.reduce( function( acc, next) {
acc[next.name] = next.id;
return acc;
}, {} )
gives
Object {abc: 12, def: 76}
.forEach()? When you're not changing the accumulator value, I don't see how reduce offers anything over other means of iteration.
reduce is a good approach for this problem, being of the type "Add something to the acc with each list entry, and in the end return acc as result".reduce() offers anything useful here over other forms of iterating. I find Artjom's answer much easier code to follow.acc does not "point to a variable" but is a variable, pointing to some memory segment (technically); the content of this segment is what we call its value, and this value is changed with each iteration (as I wrote). This is a typical reduce task. Of course, every reduce can be written as a forEach instead, with the accumulator variable declared separately, like in Artjom's solution.Iterate over all list items and add a property to the intended object.
var res = {};
list.forEach(function(item){
return res[item.name] = item.id;
});
or for general array like objects
var res = {};
Arrays.prototype.forEach.call(list, function(item){
return res[item.name] = item.id;
});
or in old school iteration
var res = {};
for(var i = 0; i < list.length; i++){
return res[list[i].name] = list[i].id;
});
.forEach on an array, why not just list.forEach()?
list.forEach. This general approach also works for objects that are accessed like arrays.Another variation, using JQuery map function ($.map)
var list = [{ 'name':"abc", 'id':12, 'addr':"random addr 0"},
{ 'name':"def", 'id':76, 'addr':"random addr 1"}];
var result = {};
$.map(list,function (i){ result[i.name] = i.id})
console.log(result);
Output:
Object {abc: 12, def: 76}
$.map should probably be $.each because you don't return anything.You could use jquery .map
I did as follows
var PAIDs = SU.Details.Actions.map(function (pa) { return pa.id; });
which gave me an array of objects with just the id
Object { abc=12, def=76}isn't valid Javascript? Do you mean{ abc:12, def:76}?Object { abc=12, def=76}in the firebug console.