how to check if variable is blank or undefined in node js [duplicate]

Question

I want to check my data is blank or undefined but my if block execute even my data is not blank ...

Code is :

router.post('/addNewGrade',function(req , res){ 
    var errorMsg = [];  
    console.log(req.body.gradeName)
    if(req.body.gradeName == '' || req.body.gradeName === undefined){
        errorMsg.push("please enter grade name");
    }
    if(req.body.gradeDescription == '' || req.body.gradeDescription === undefined){
        errorMsg.push("please enter description about your grade");
    }
    if(errorMsg !=''){
        res.send({errorMessage :errorMsg}); 
        return;
    }

});

what is the best way to check variable is undefined or not

Please log the values of req.body.gradeName etc. to confirm their value. — user663031
– user663031, Commented Jan 19, 2016 at 15:15

gradorade · Accepted Answer · 2016-01-19 14:16:26Z

19

Because an undefined variable is "falsey", you can simple do

if (body.req.gradeName) {
  // do normal stuff
} else {
  // do error stuff
}

Or if you don't need to do anything if it is defined, then you can do

if (!(body.req.gradeName)) {
 // do error stuff 
}

answered Jan 19, 2016 at 14:16

gradorade

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5 Comments

user663031 Over a year ago

Sure, but how does this explain the behavior reported by the OP?

gradorade Over a year ago

Apologies! I missed that. I agree with you torazaburo, I would like to see what the console.log value of gradeName is.

Frank Over a year ago

CAREFUL with this, if body.req.gradeName is false ("false" or false), you're not in an error situation, false can be a value too.

Balint Bako Over a year ago

This will go to the error branch for several "normal" values

cmnardi Over a year ago

If body.req.gradeName cames with '0' will do the 'error stuff', sometimes is not the expectd behavior

Tewdyn · Accepted Answer · 2016-01-19 15:14:25Z

13

You can do it like this

if(typeof variable === 'undefined'){
//Variable isn't defined
}

edited Jan 19, 2016 at 15:14

answered Jan 19, 2016 at 14:02

Tewdyn

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Comments

Ashutosh Jha · Accepted Answer · 2016-01-19 15:16:37Z

-2

it is working

if(req.body.gradeDescription == '' || req.body.gradeDescription === undefined)

edited Jan 19, 2016 at 15:16

user663031

answered Jan 19, 2016 at 14:04

Ashutosh Jha

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1 Comment

Icepickle Over a year ago

that seems to be the exact same thing as your starting post...

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