What does [literal] in [array/object] mean?

Question

What does the following syntax mean:

1 in [1,2,3,5]

I know it doesn\'t search for 1 in the array. But what does it do?

I\'ve seen it u

Answer 1

It's used to iterate JavaScript objects.

This loop will iterate through each "key" in the object.

Its common usage is iterate through such objects:

var Car = { color: "blue", price: 20000 };
for (var key in Car)
    console.log("Propery " + key + " of Car is: " + Car[key]);

Live test case - check Chrome/Firefox JavaScript console to see the output.

When used for plain arrays, each "key" will be the index.. for example:

var nums = [20, 15, 30]
for (var key in nums)
    console.log("Propery " + key + " of array is: " + nums[key]);

Will show the keys as 0, 1 and 2. Updated fiddle for such case.