check null,empty or undefined angularjs

Question

I am creating a project using angularjs.I have variable like

$scope.test = null
$scope.test = undefined
$scope.test = \"\"

I want to check all

Answer 1

You can do

if($scope.test == null || $scope.test === ""){
  // null == undefined
}

if false, 0 and NaN can also be considered as false values you can just do

if($scope.test){
 //not any of the above
}

Answer 2

if($scope.test == null || $scope.test == undefined || $scope.test == "" ||    $scope.test.lenght == 0){

console.log("test is not defined");
}
else{
console.log("test is defined ",$scope.test); 
}

Answer 3

You can also do a simple check using function,

$scope.isNullOrEmptyOrUndefined = function (value) {
    return !value;
}

Answer 4

A very simple check that you can do:

Explanation 1:

if (value) {
 // it will come inside
 // If value is either undefined, null or ''(empty string)
}

Explanation 2:

(!value) ? "Case 1" : "Case 2"

If the value is either undefined , null or '' then Case 1 otherwise for any other value of value Case 2.

Answer 5

You can do simple check

if(!a) {
   // do something when `a` is not undefined, null, ''.
}

Answer 6

You can use angular's function called angular.isUndefined(value) returns boolean.

You may read more about angular's functions here: AngularJS Functions (isUndefined)