indexOf() + 1 vs indexOf() != -1

Question

When checking for existence of a substring I have been doing this:

var that = "ok hello cool";    
if( that.indexOf('hello') + 1 ) {
}

Instead of:

if( that.indexOf('hello') != -1 ) {
}

Am I overlooking something or is there a reason not to do this.

Update:

Yes, I was indeed unaware of the even simpler method of:

if ( ~that.indexOf( 'hello' ) ) {

}

You can read about the ~ bitwise operator and the other queer bitwise operators here: https://developer.mozilla.org/en/JavaScript/Reference/Operators/Bitwise_Operators

Answer 1

Here is the most seen way:

if ( ~that.indexOf( 'hello' ) ) {
}

The ~ operator does some magic and transforms only -1 in 0, thus it's the only falsy value.

Answer 2

Well, I believe the second one is more obvious what's going on...

if( that.indexOf('hello') != -1 ) {
}

That's all to it however, both expressions are valid and perfectly ok.