JQuery to determine whether the terminal is iOS or android/jquery processing background images can not fill the screen

Determine the terminal and perform different processing methods (functions) for the corresponding terminal

$ ("#btn_download"). Click (function () {            varU =navigator.useragent; varisandroid = U.indexof (' Android ') >-1 | | U.indexof (' Adr ') >-1;//Android Terminal            varIsios =!! U.match (/\ (i[^;] +;( U;)? Cpu.+mac OS x/);//iOS terminal$ ("#lucencyBg"). Show (); if(isandroid) {//Android Terminal processing functionAlert (' is Android: ' +isandroid); }Else if(Isios) {//iOS terminal processing functionsAlert (' is iOS: ' +Isios); }Else{alert ("Other Browsers"); }        });

Attached: jquery processing background picture does not fill the screen:

$ ("#_main"). Height (window.innerheight);         // two options available, available on request        // window.screen.height        // window.innerheight                //

So the CSS code does not have to write height, but to add a few words of CSS:

#_main {    width: 100%;     background: URL (".. /images/qrbg.png ") 0 0 no-repeat;    /* need to add the following code */     background-size: 100% auto;     display: flex;     justify-content: center;}

JQuery to determine whether the terminal is iOS or android/jquery processing background images can not fill the screen