AngularJS- Check A value is undefined or null

Question

Okay! New to AngularJS. Here is my controller code to check if a value is undefined or null.

var configId=$routeParams.confiId;
    angular.isUndefinedOrNull = function(configId){ return angular.isUndefined(configId) || configId === null};
    if(angular.isUndefinedOrNull) {
        alert(configId);
        alert("true");
    } else {
        alert("false");
    }

And it always alerts with true. So I tried alerting configId. If the value is there, it alerts the value otherwise it is alerting undefined. Not going to else part as condition is always true. What is wrong here?

Sorry @KhanhTO it was working. I only replaced the if and alerted wrong. :) — iCode
– iCode, Commented Feb 8, 2014 at 6:18

godfrzero · Accepted Answer · 2014-02-08 06:15:10Z

10

if(angular.isUndefinedOrNull) is basically checking to see if angular.isUndefinedOrNull is truthy. Since angular.isUndefinedOrNull is a function, this will always be true.

Try if( angular.isUndefinedOrNull(configId) ), which checks if the value returned by angular.isUndefinedOrNull is truthy. This will alert true if the value returned by angular.isUndefinedOrNull() is truthy, and false otherwise.

answered Feb 8, 2014 at 6:15

godfrzero

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5 Comments

Deryck Over a year ago

To add to @godfrzero's answer here, you also want to be aware that function(configId) {...} isn't passing configId in, it's declaring it as a new variable in the scope of that function. You still need to pass it when you call the function. So instead of if( angular.isUndefinedOrNull() ) you want if( angular.isUndefinedOrNull(configId) )

Deryck Over a year ago

ah it seems we had similar thoughts. Good, all is well now.

Alex Coroza Over a year ago

angular.isUndefinedOrNull is really a function in AngularJS? What version? I can't see it in API Reference in AngularJS' site

godfrzero Over a year ago

@AlexCoroza Old question, but seems like it's a function iProgrammer defined and not a part of Angular. iProgrammer, please correct me if I'm wrong?

ykadaru Over a year ago

@boi_echos I believe it's just angular.isUndefined now. docs.angularjs.org/api/ng/function/angular.isUndefined

Cheezy Code · Accepted Answer · 2016-03-21 07:25:34Z

1

You can use basic javascript check like

if(nameOfVariable) //Returns false if variable has null or blank or undefined as value
{

} 
else
{

}

Cheers from CheezyCode

answered Mar 21, 2016 at 7:25

Cheezy Code

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2 Comments

yms Over a year ago

This is not useful if 0 or false are possible valid values of your variable.

Cheezy Code Over a year ago

@yms - Agreed with your comment.

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