How to pass function to compare items?

Question

I would like to pass a comparer into a function and not sure if this is possible with Javascript. There is an IComparer concept in C# that does this. Can this be done in Javascript?

function someAction (comparer) {
    var newList = [];
        $.each(list, function (index, item) {
            if comparer on item is true then { //psuedo code
                newList.push(item);
            }
        });
}

someAction(item.PropA > 5);

Answer 1

function someAction (comparer) {
    var newList = [];
        $.each(list, function (index, item) {
            if (comparer(item)) {
                newList.push(item);
            }
        });
}
someAction(function (item) { return item.PropA > 5 });

PS: as @BrokenGlass suggested, you can avoid reinventing the wheel and use the filter function.

Answer 2

Just call the function:

  if (comparer(item)) { ... }

All references to functions in JavaScript are equivalent, so any reference can be used to invoke a function in the same way any other reference can be used. Functions are first-class objects, in other words.

Answer 3

You might be looking for filter, which already exists in JavaScript:

var newList = list.filter(function(item) {
  return item.PropA > 5;
});