javascript's way of determining whether a variable has a value
- 2020-06-01 08:08:43
- OfStack
This example shows how javascript determines whether a variable has a value. Share with you for your reference. The specific analysis is as follows:
Such as:
var a = null;
var b = undefined;
These two cases count as no values
if(a !== null && a !== undefined) {
//
}
// Why not use it alone if(a !== null) { // }
var a;
a !== null; // true
// Why not use it alone if(a !== undefined) { // }
var a = null;
a !=== undefined; // true
I hope this article has been helpful to your javascript programming.