Javascript Object: iterating over properties [duplicate]

This question already has answers here: Iterate over Object Literal Values (8 answers) Each for object? [duplicate] (3 answers) Closed 2 years ago. 开发者_如何转开发

I have a variable, which, when printed to console, looks like this:

Object { PK-34={...}, PK-35={...}}

I'm adding a size method to this variable:

Model_value.size = function(obj) {
    var size = 0, key;
    for (key in obj) {
    if (obj.hasOwnProperty(key)) size++;
    }
    return size;
};

This method returns 0, and iterating over those properties using:

for (foo in Model_value)
{
  //...
}

does not work.

How would I iterate over those PK-34, PK-35 properties?

---

If size ends up being zero, apparently the object in question is inheriting those properties from its prototype. In that case, it means you don't want the hasOwnProperty check.

Example:

var Model_value = {};
Model_value.size = function(obj) {
    var size = 0, key;
    for (key in obj) {
    if (obj.hasOwnProperty(key)) size++;
    }
    return size;
};
Model_value.sizeInherited = function(obj) {
    var size = 0, key;
    for (key in obj) {
      size++;
    }
    return size;
};

function Foo() {
}
Foo.prototype["PK-34"] = {
  name: "I'm PK-34"
};
Foo.prototype["PK-35"] = {
  name: "I'm PK-35"
};

display("Model_value.size(new Foo()) = " + Model_value.size(new Foo()));
display("Model_value.sizeInherited(new Foo()) = " + Model_value.sizeInherited(new Foo()));

var f = {
  "PK-34": {name: "I'm PK-34"},
  "PK-35": {name: "I'm PK-35"}
};

display("Model_value.size(f) = " + Model_value.size(f));
display("Model_value.sizeInherited(f) = " + Model_value.sizeInherited(f));

var bar = new Foo();
bar["PK-36"] = {name: "I'm PK-36"};

display("Model_value.size(bar) = " + Model_value.size(bar));
display("Model_value.sizeInherited(bar) = " + Model_value.sizeInherited(bar));

Live copy

In the first case (new Foo()), the new object created by Foo has no properties of its own (only inherited ones) and so size ends up being 0 whereas sizeInherited is 2 (because it inherits two properties from its prototype).

In the second case, because f has its own PK-34 and PK-35 properties, its size is 2. It inherits no properties from its prototype, and so sizeInherited is also 2.

In the third case, bar has both two inherited properties and one property of its own, so size is 3 and sizeInherited is 2.

---

Update: The edit seems to change the question a bit. If you're trying to iterate over the properties in Model_value, then you don't want to accept an argument, you want to use this:

To find how many own properties it has:

Model_value.size = function() {
    var size = 0, key;
    for (key in this) {
        if (this.hasOwnProperty(key)) size++;
    }
    return size;
};

To find how many properties total it has (including inherited ones):

Model_value.size = function() {
    var size = 0, key;
    for (key in this) {
        size++;
    }
    return size;
};

Example:

function Model() {
}
Model.prototype["PK-34"] = {
  name: "I'm PK-34"
};
Model.prototype["PK-35"] = {
  name: "I'm PK-35"
};

var Model_value = new Model();

Model_value.size = function() {
  var size = 0, key;
  for (key in this) {
      if (this.hasOwnProperty(key)) size++;
  }
  return size;
};

Model_value.sizeInherited = function() {
  var size = 0, key;
  for (key in this) {
      size++;
  }
  return size;
};

display("Model_value.size() = " + Model_value.size());
// ^-- returns 2 ("size" and "sizeInherited")

display("Model_value.sizeInherited() = " + Model_value.sizeInherited());
// ^-- returns 4 ("PK-34", "PK-35", "size", and "sizeInherited")

Live copy

Note that the functions we've added to Model_value are assigned to properties, and so they show up in the totals.