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

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. — , Jan 19 '16 at 15:15

score 20 · Accepted Answer · answered Jan 19 '16 at 14:16

20

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 '16 at 14:16

gradorade

294
1
9

Sure, but how does this explain the behavior reported by the OP? – Jan 19 '16 at 15:16
Apologies! I missed that. I agree with you torazaburo, I would like to see what the console.log value of gradeName is. – gradorade Jan 19 '16 at 15:24
1

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. – Frank Feb 17 '20 at 15:53

Tewdyn · Answer 2 · 2016-01-19T15:14:25.870

4

You can do it like this

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

edited Jan 19 '16 at 15:14

answered Jan 19 '16 at 14:02

Tewdyn

627
3
15

score -2 · Answer 3 · edited Jan 19 '16 at 15:16

-2

it is working

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

edited Jan 19 '16 at 15:16

answered Jan 19 '16 at 14:04

Ashutosh Jha

166
1
2
10

1

that seems to be the exact same thing as your starting post... – Icepickle Jan 19 '16 at 14:08

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

3 Answers3

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