Javascript cross-browser attribute Judgment Method

Today, when I write code, I find it very error-prone. When declaring variables, we often have different API definitions for different browsers, and then use the following statement to determine which attribute, for example:
Copy codeThe Code is as follows: var fullscreenElement = document. javasfullscreenelement | document. webkitFullscreenElement | document. fullscreenElement;
Use | to check which attribute to use.
However, be careful when javascript values are considered as conditions.
For example:
Copy codeCode: var sLeft = window. screenLeft | window. screenX; // firefox use screenX
Console. log (sLeft );
This Code expects that screenLeft will return window. screenLeft, while firefox will return window. screenX.
However, if screenLeft is equal to 0, it will enter the | condition, and then gg.

Therefore, it is recommended to use hasOwnProperty or typeof to judge the value in an Orthodox way.
Copy codeCode: var sLeft = window. screenLeft;
If (! Window. hasOwnProperty ('screenleft') sLeft = window. screenX;