I am creating a project using angularjs.I have variable like
$scope.test = null
$scope.test = undefined
$scope.test = ""
I want to check all null,undefined and empty value in one condition
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7 Answers
just use -
if(!a) // if a is negative,undefined,null,empty value then...
{
// do whatever
}
else {
// do whatever
}
this works because of the == difference from === in javascript, which converts some values to "equal" values in other types to check for equality, as opposed for === which simply checks if the values equal. so basically the == operator know to convert the "", null, undefined to a false value. which is exactly what you need.
2 Comments
Charleshaa
I would be careful with that when dealing with booleans. Using
$scope.$watch() for example, you want to check if the new value is undefined or null, but if that value is a boolean, using your solution will not work.
Jon Senchyna
You also want to be careful with numbers, as you may want to catch undefined and null, but not 0.
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
}
Comments
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);
}
Comments
You can use angular's function called angular.isUndefined(value) returns boolean.
You may read more about angular's functions here: AngularJS Functions (isUndefined)
Comments
You can do simple check
if(!a) {
// do something when `a` is not undefined, null, ''.
}
Comments
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.
Comments
You can also do a simple check using function,
$scope.isNullOrEmptyOrUndefined = function (value) {
return !value;
}
2 Comments
Théophile
The function name is misleading, since
value might be 0.
Hatem Ahmed
this function will return the opposite of what you are passing. regardless of data type