How can one check if a variable is empty in Angular 2? I know that there are native ways such as
if (myVar === null) {do stuff}
but I am looking for something like Angular 1 had such as
if (angular.isEmpty(variable)) { do stuff }.
Q How do check if variable is empty using Angular 2?
Lets say we have a variable called x, as below:
var x;
following statement is valid,
x = 10;
x = "a";
x = 0;
x = undefined;
x = null;
1. Number:
x = 10;
if(x){
//True
}
and for x = undefined or x = 0 (be careful here)
if(x){
//False
}
2. String x = null , x = undefined or x = ""
if(x){
//False
}
3 Boolean x = false and x = undefined,
if(x){
//False
}
By keeping above in mind we can easily check, whether variable is empty, null, 0 or undefined in Angular js. Angular js doest provide separate API to check variable values emptiness.
if( myVariable )
{
//mayVariable is not :
//null
//undefined
//NaN
//empty string ("")
//0
//false
}
You can play here with different types and check the output,
export class ParentCmp {
myVar:stirng="micronyks";
myVal:any;
myArray:Array[]=[1,2,3];
myArr:Array[];
constructor() {
if(this.myVar){
console.log('has value') // answer
}
else{
console.log('no value');
}
if(this.myVal){
console.log('has value')
}
else{
console.log('no value'); //answer
}
if(this.myArray){
console.log('has value') //answer
}
else{
console.log('no value');
}
if(this.myArr){
console.log('has value')
}
else{
console.log('no value'); //answer
}
}
}
user:Array[]=[1,2,3];
if(this.user.length)
{
console.log("user has contents");
}
else{
console.log("user is empty");
}
It depends if you know the given variable Type. If you expect it to be an Object than you could check if myVar is an empty Object like this:
public isEmpty(myVar): boolean {
return (myVar && (Object.keys(myVar).length === 0));
}
Otherwise: if (!myVar) {}, should do the job
Angular 4 empty data if else
if(this.data == 0)
{
alert("Null data");
}
else
{
//some logic
}
