Javascript 如何在firefox移动浏览器中打开桌面视图

如何使用查看端口在mozila移动浏览器中打开桌面视图。我试着用mozila mobile browse打开桌面视图。我在用这个

// Store the meta element
var viewport_meta = document.getElementById('viewport-meta');

// Define our viewport meta values
    var viewports = {
    default: viewport_meta.getAttribute('content'),
    landscape: 'width=990'
};

// Change the viewport value based on screen.width
var viewport_set = function() {
    if ( screen.width > 768 )
        viewport_meta.setAttribute( 'content',viewports.landscape );
    else
        viewport_meta.setAttribute( 'content', viewports.default );
}

// Set the correct viewport value on page load
    viewport_set();

// Set the correct viewport after device orientation change or resize
window.onresize = function() { 
    viewport_set(); 
}

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请告诉我们您在尝试时使用的代码。请告诉我们您在尝试时使用的代码。