# & operators into if instrucion
**URL:** https://discourse.nodered.org/t/operators-into-if-instrucion/10171
**Category:** General
**Created:** [15 April 2019 13:24 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171 "2019-04-15T13:24:10Z")
**Posts on this page:** 12
**Page:** 1
### Author:  [@GiovanniG](https://discourse.nodered.org/u/GiovanniG)
#### Post date: [15 April 2019 13:24 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/1 "2019-04-15T13:24:10Z")
Hi mates, after a couple of hours I figured out what didn't work. For me it's something illogic, and I'm afraid to loose in future more time on something similar:
Supposing we have a byte IO1\_B, the result of the read of I/O chip connected to some lines. I need to test the first bit, ad do something according to it
Why if (IO1\_B & 0x1) gives a proper result
and if (IO1\_B & 0x1 == 0) or if (IO1\_B & 0x1 === 0) doesn't give the opposite result? where is the problem here? Should I writ if (IO1\_B & 0x1 === false)? or if ((IO1\_B & 0x1) === 0) ?
Thank you
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### Author:  [@zenofmud](https://discourse.nodered.org/u/zenofmud)
#### Post date: [15 April 2019 13:35 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/2 "2019-04-15T13:35:38Z")
try a google search using `javascrippt multiple comparisons`
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### Author:  [@GiovanniG](https://discourse.nodered.org/u/GiovanniG)
#### Post date: [15 April 2019 21:48 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/3 "2019-04-15T21:48:11Z")
Thank you, unfortunately not easy to find exactly my case..
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 April 2019 21:57 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/4 "2019-04-15T21:57:28Z")
Bitwise operators return a number.
You can get to grips with them [Here](https://www.w3schools.com/js/js_bitwise.asp)
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### Author:  [@GiovanniG](https://discourse.nodered.org/u/GiovanniG)
#### Post date: [15 April 2019 22:02 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/5 "2019-04-15T22:02:14Z")
thanks for your answer,, why 0 is not a number?
(IO1\_B & 0x1) works, if the first bit of IO1\_B is 1 i can execute something, or better.. my goal is to check if it is 0, so I use the "else" command.
now why (IO1\_B & 0x1 == 0) doesn't work?
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 April 2019 22:16 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/6 "2019-04-15T22:16:40Z")
Operator precidance.
Try `((IO1_B & 0x1) == 0)`
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### Author:  [@GiovanniG](https://discourse.nodered.org/u/GiovanniG)
#### Post date: [16 April 2019 18:32 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/7 "2019-04-16T18:32:14Z")
thank you, now it's more clear how javascript works. In C the precedence is on operators, not on the =, there is no sense to put priority on =
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [16 April 2019 20:12 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/8 "2019-04-16T20:12:40Z")
You right however...
== is an operator.
= Is assignment.
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### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [16 April 2019 21:21 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/9 "2019-04-16T21:21:45Z")
I am not absolutely certain but I think you will find that C is exactly the same as javascript in this case, so
`a & b == 0`
will be interpreted as
`a & (b == 0)`
in both languages.
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### Author:  [@GiovanniG](https://discourse.nodered.org/u/GiovanniG)
#### Post date: [20 April 2019 11:54 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/10 "2019-04-20T11:54:28Z")
Thank you for help! SInce now I always had the feeling that compiler will do everything before == and after it, it has much more logic, by the way it could be just a "good" compiler, to me )
I've got the lesson to always use pharentesis, it will make me much less crazy )
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### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [20 April 2019 12:40 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/11 "2019-04-20T12:40:25Z")
Consider what you might expect if you used
`a == 0 & b == 0`
You might expect it to interpret this as
`(a==0) & (b==0)`
In which case `==` has to be performed before `&`
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### Author:  [@GiovanniG](https://discourse.nodered.org/u/GiovanniG)
#### Post date: [20 April 2019 12:51 UTC](https://discourse.nodered.org/t/operators-into-if-instrucion/10171/12 "2019-04-20T12:51:43Z")
I understand, I got the reason. Good bless pharentesis