The problem is that undefined compared to null using == gives true.
The common check for undefined is therefore done like this:
typeof x == "undefined"
this ensures the type of the variable is really undefined.
More Related Contents:
- Running python on client side
- Javascript object literal: what exactly is {a, b, c}?
- Promise – is it possible to force cancel a promise
- Include jQuery in the JavaScript Console
- Iterate through object properties
- Palindrome check in Javascript
- Getting the return value of Javascript code in Selenium
- Expose jQuery to real Window object with Webpack
- getElementById() returns null even though the element exists [duplicate]
- How do I convert String to Number according to locale (opposite of .toLocaleString)?
- How can I show a hidden div when a select option is selected?
- With JavaScript, can I change the Z index/layer of an SVG element?
- Decode UTF-8 with Javascript
- pass post data with window.location.href
- Why and when to use default export over named exports in es6 Modules?
- How to get the tag HTML with JavaScript / jQuery?
- How to make Google Chrome JavaScript console persistent?
- How to make jQuery to not round value returned by .width()?
- How to set ChartJS Y axis title?
- callback function meaning
- Object.getOwnPropertyNames vs Object.keys
- When value is assigned to components state, why console.log prints the previous state?
- javascript: convert two dimensional array to array of objects using the first ‘row’ to define properties
- Force showing the “Save as” dialog box when downloading a file
- Adding text to beginning of each array element
- Handling multiple files from an input element in an array with Google Apps Script
- Which types of queues are in event loop?
- Reconciling ASP.NET script bundles and source maps
- Why can’t I use `allAuthenticatedUsers` for my Firebase Cloud Function?
- blocked a frame of origin “null” from accessing a cross-origin frame – chrome