js get the browser's zoom state, state the percentage of scaling the upper right corner of the browser

First, here's browser status refers to the page the user clicks on the top left corner of the browser zoom plus / minus generated overall change into small cases (shortcut: Ctrl + Plus or Ctrl + Minus or Ctrl + scroll wheel up and down)

Codes are as follows:

If detectZoom function return value is the default zoom level is 100, more than 100 is enlarged, less than 100 is reduced.

 1 function detectZoom (){
 2   var ratio = 0,
 3     screen = window.screen,
 4     ua = navigator.userAgent.toLowerCase();
 5   
 6    if (window.devicePixelRatio !== undefined) {
 7       ratio = window.devicePixelRatio;
 8   }
 9   else if (~ua.indexOf('msie')) {
10     if (screen.deviceXDPI && screen.logicalXDPI) {
11       ratio = screen.deviceXDPI / screen.logicalXDPI;
12     }
13   }
14   else if (window.outerWidth !== undefined && window.innerWidth !== undefined) {
15     ratio = window.outerWidth / window.innerWidth;
16   }
17     
18    if (ratio){
19     ratio = Math.round(ratio * 100);
20   }
21     
22    return ratio;
23 };

var ratio = detectZoom () 

// Print scale value 
the console.log (ratio) 

// determines whether scaling 

IF (ratio> 100 ) { 
  the console.log ( "amplification la" )   
} the else  IF (ratio <100 ) { 
    Console. log ( "narrowing" ) 
} the else { 
  the console.log ( "100%" )       
}