How to fix the display of the background?

When I'm on his website use
<meta name="viewport" content="width=device-width, initial-scale=1">

the background displays only half. To display the background I use(PC only)
$('body').css('background', 'url("img/background.jpg")').css('background-repeat', 'no-repeat').css('background-size', '100% 100%');

here is the website
April 3rd 20 at 17:12
1 answer
April 3rd 20 at 17:14
Try this in CSS:

body { 
background: url(img/background.jpg) no-repeat scroll center center/cover;

And I do not understand why using Jquery to set the background for Body.
because after preblauer remained the same background - ole_Schuster commented on April 3rd 20 at 17:17

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