I want to know what the difference is between null and undefined in JavaScript....
Why is null considered an object in JavaScript? Is checking if ( object == null ) Do something the same as if ( !object ) Do something ? And also: What is the difference between null and undefined?...
We are frequently using the following code pattern in our JavaScript code if (typeof(some_variable) != 'undefined' && some_variable != null) { // Do something with some_variable } Is there a less verbose way of checking that...How can I check for null values in JavaScript? I wrote the code below but it didn't work. if (pass == null || cpass == null || email == null || cemail == null || user == null) { alert("fill all columns"); return false;...As you may know, in JavaScript '' + null = "null" and '' + undefined = "undefined" (in most browsers I can test: Firefox, Chrome and IE). I would like to know the origin of this oddity (what the heck was in the head on...
How do I verify the existence of an object in JavaScript? The following works: if (!null) alert("GOT HERE"); But this throws an Error: if (!maybeObject) alert("GOT HERE"); The Error: maybeObject is not defined....I've come across the following code: function test(data) { if (data != null && data !== undefined) { // some code here } } I'm somewhat new to JavaScript, but, from other questions I've been reading here, I'...I'm using a system to alert users when a major update has happened to a site, and I do it with LocalStorage, when I made the system, I made the system check if tip was "null", then set "tip" to true when they got the alert. Now, I...
While trying to debug I am get the 'length' null error with this line. It is written just like the book instructed, so I don't understand why it is giving me the error? Thanks, =) if (capital.length < 1) { ( here is the full code...null and undefined don't have a toString or valueOf method. Afaik using String calls the toString method of its parameter (e.g. String({}) => [object Object]). Why do String(null) or String(undefined work then? It doesn't implicitly do O...©2020 All rights reserved.