Why does the following returns undefined?
var global_vars =
{
countNumOfProperties :
function (obj)
{
var count = 0;
for (var k in obj) {
if (obj.hasOwnProperty(k)) {
++count;
}
return count;
}
}
};
var DS =
{
file_types_lookup : {}
};
global_vars.countNumOfProperties(DS.file_types_lookup)
Because the object has no own properties, so the for loop has no iterations that are executed, and no return statement gets executed.
I guess you misplaced a }:
var count = 0;
for (var k in obj) {
if (obj.hasOwnProperty(k)) {
++count;
}
}
return count;
The return statement is inside the loop so is never reached.
for (var k in obj) {
if (obj.hasOwnProperty(k)) {
++count;
}
return count;
}
should probably be
for (var k in obj) {
if (obj.hasOwnProperty(k)) {
++count;
}
}
return count;
That way, each property will be checked before the sum is returned.
As written, the function will return
1 to indicate that the first enumerable property is an own property, or0 to indicate that there are no own properties but there are enumerable inherited properties, orundefined to indicate that there are no enumerable properties own or otherwise.Observe what happens when you pass it an object that does have properties:
> global_vars.countNumOfProperties({foo: 1})
1
> global_vars.countNumOfProperties({foo: 1, bar: 2})
1
> global_vars.countNumOfProperties({foo: 1, bar: 2, baz: 3})
1
The problem is that you put the return statement inside the loop. It will be executed the first time the loop body executes, returning 1 and ending the loop. However, if the loop body never runs (because there are no properties) it never gets run and the function returns the default value, undefined.
You just need to move return down by one line, outside the loop.
The return count; statement should be outside of the for loop.
