"in" statement in Javascript/jQuery

Question

Does Javascript or jQuery have sometime like the "in" statement in Python?

"a" in "dea" -> True

Googling for the word in is hopeless :(

Answer 1

It does have an in operator but is restricted to object keys only:

var object = {
    a: "foo",
    b: "bar"
};

// print ab
for (var key in object) {
    print(key);
}

And you may also use it for checks like this one:

if ("a" in object) {
    print("Object has a property named a");
}

For string checking though you need to use the indexOf() method:

if ("abc".indexOf("a") > -1) {
    print("Exists");
}

Answer 2

How about indexOf?

Answer 3

Sounds like you need regular expressions!

if ("dea".match(/a/))
{ 
    return true;
}

Answer 4

you would need to use indexOf

e.g

"dea".indexOf("a"); will return 2

If its not in the item then it will return -1

I think thats what you are after.

Answer 5

With the indexOf function, you can extend the String like such:

String.prototype.in = function (exp) {
    return exp.indexOf(this) >= 0;
}

if ("ab".in("abcde")) { //true

}