In javascript I get error ASP.NET Ajax client-side framework failed to load

Question

我在JavaScript中遇到错误

if (typeof(Sys) === 'undefined') throw new Error('ASP.NET Ajax client-side framework failed to load.');

Answer 1

我认为typeof可以用作

if(typeof Sys== "undefined")

Answer 2

Triple equals, === , in javascript is to test for the same type or object.

Change it to double equals, == instead. This will test for the value instead of object equality.

Possible duplicate of these questions:

• How to determine equality for two JavaScript objects?
• Object comparison in JavaScript
• Also this site really explains === well.