indexOf() + 1 vs indexOf() != -1 [closed]

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Closed 9 years ago.

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

@RussellBorogove Nothing. It's totally valid. ~ is a lot cleaner than >= 0. — iambriansreed, Commented Jul 23, 2012 at 21:07

Florian Margaine · Accepted Answer · 2012-07-23 19:03:12Z

12

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.

answered Jul 23, 2012 at 19:03

Florian Margaine

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1

\$\begingroup\$ That is neat, never seen that. \$\endgroup\$
– George Mauer
Commented Jul 23, 2012 at 19:03
2

\$\begingroup\$ @Florian MDN says: Inverts the bits of its operand. WTH does that mean? \$\endgroup\$
– iambriansreed
Commented Jul 23, 2012 at 19:05
1

\$\begingroup\$ Ok, that's not really important to understand here. All you need to understand is that ~-1 === 0 (false for not found) and ~anythingelse !== 0 (true for found) \$\endgroup\$
– Esailija
Commented Jul 23, 2012 at 19:06
\$\begingroup\$ @iambriansreed It's working on the bits of the number. For example, 2 in base 10 is 0010 in base 2. Well, ~ inverts all the bits. But yeah, as Esailija says, it's not really important to know, you probably won't ever use it except for this case. \$\endgroup\$
– Florian Margaine
Commented Jul 23, 2012 at 19:07
9

\$\begingroup\$ I think that this not the best way to make code readable. Why using bitwise operator to create a condition? != -1 is used in many languages and it is the simplest and most readable method. \$\endgroup\$
– Sulthan
Commented Jul 24, 2012 at 9:48

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James Khoury · Accepted Answer · 2012-08-02 02:33:52Z

13

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.

James Khoury

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answered Jul 23, 2012 at 18:59

walther

3582 silver badges9 bronze badges

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