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Website⁢ Code Snippets Focus ⁤on Mobile Detection,⁣ Country Flags, and Lazy Loading

Website developers employ various JavaScript techniques to⁢ optimize⁣ user experience based on device type, location, and network conditions.Recent code snippets reveal strategies ⁣for mobile device detection, displaying⁤ country-specific flags, and implementing lazy loading for images and videos.

Mobile Device Detection

One common task is‍ detecting whether a user ⁣is browsing on a mobile phone.The provided code uses a regular expression to check‌ the user agent string. If a match ⁣is found, a ⁢boolean variable, is_phone, is set to true.

function is_mobile() {
    let check = false;
    (function(a){
        if(/android|avantgo|blackberry|blazer|compal|elaine|fennec|hiptop|iemobile|ip(ad|hone|od)|iris|kindle|lge |maemo|midp|mmp|mobile.+firefox|netfront|opera m(ob|in)i|palm( os)?|phone|p(ixi|re)/i.test(a)||/1207|6310|6590|3gso|4thp|50[1-6]i|770s|802s|a wa|abac|ac(er|oo|s-)|ai(ko|rn)|al(av|ca|co)|amoi|an(ex|ny|yw)|aptu|ar(ch|go)|as(te|us)|attw|au(di|-m|r |s )|avan|be(ck|ll|mi)|bi(et|rd)|bl(ac|az)|br(e|v)w|bumb|bw-(n|u)|c55/|capi|ccwa|cdm-|cell|chtm|cldc|cmd-|co(mp|nd)|craw|da(it|ll|ng)|dbte|dc-s|devi|dica|dmob|do(c|p)o|ds(12|-d)|el(41|io)|elks|er(ic|kit)|esl8|ez([4-7]0|os|wa|ze)|fetc|fly(-|_)|g1 u|g50|ga(mb|e)|gc(ea|me|nf|nw)|gener|germ|gh(cl|en|ie)|gl(mm|ng|on)|go(mo|r)i|gr(ad|un)|haie|hcit|hd(m|p|t)|hei-|hi(pt|ta)|hp( i|ip)|hs-c|ht(c(-| |_|a|g|p|s|t)|tp)|hu(aw|tc)|i-(20|go|ma)|i230|iac( |-|/)|ibro|idea|ig01|ikom|im1k|indc|inno|ipaq|iris|ja(t|v)a|jbro|jemu|jigs|kddi|keji|kgt( |/)|klon|kpt |kwc-|kyo(c|k)|le(no|xi)|lg( g|/(kg|t|u)|50|54|-[a-w])|libw|lynx|m1-w|m3ga|m50|ma(te|ui|xo)|mc(01|21|ca)|m-cr|me(rc|ri)|mi(o8|oa|ts)|mmef|mo(01|02|bi|de|do|t(-| |o|v)|zz)|mt(50|poc)|mx(ec|rf|tf)|m-v3|mz(ut|uz)|n0(0|2)|n20(e|t)|n30(0|2)|n50(0|2|5)|n70(0|1|2)|nec-|nemu|nike|noki|nzph|o2im|op(ti|wv)|oran|owg1|p800|pan(a|d|t)|pdxg|pg(13|-([1-8]|c))|phil|pire|pl(ay|uc)|pn-2|po(ck|rt|se)|prox|psio|pt-g|qa-a|qc(07|12|21|32)|qtek|r380|r600|raks|rim9|ro(ve|zo)|s55/|sa(ge|ma|mm|ms|ny|va)|sc(01|h-|oo|p-)|sdk/|se(c(-|0|1)|47|mc|nd|ri)|sgh-|shar|sie(-|m)|sk-0|sl(45|id)|sm(al|ar|b3|it|t5)|so(ft|ny)|sp(01|h-|v-|v )|sy(01|mb)|t2(18|50)|t6(00|10|18)|ta(gt|lk)|tcl-|tdg-|tel(i|m)|tim-|t-mo|to(pl|sh)|ts(70|m-|m3|m5)|tx-9|up(.b|g1|si)|utst|v400|v750|veri|vi(rg|te)|vk(40|5[0-3]|-v)|vm40|voda|vulc|vx(52|53|60|61|70|80|81|83|85|98)|w3c(-| )|webc|whit|wi(g |nc|nw)|wmlb|wonu|x700|yas-|your|zeto|zte-/i.test(a.substr(0,4))) {
            check = true;
        }
    })(navigator.userAgent||navigator.vendor||window.opera);
    return check;
}
        

This function is then used to ​conditionally ​load JavaScript files, potentially serving different⁤ scripts to mobile and desktop users.

Dynamic JavaScript Loading

The code includes functions to load JavaScript files dynamically.‌ The load_js function creates a script element, sets its ⁢source, and ⁢appends it to the document’s head. A​ load_js_fast function ‌wraps ⁤this, ‍ensuring that the script is only loaded if the user is not⁤ identified as⁣ a bot.

function load_js(js_src) {
    var s = document.createElement("script");
    s.type = "text/javascript";
    s.src = js_src;
    document.head.appendChild(s);
}

function load_js_fast(js_src) {
    if (!is_bot()) {
        load_js(js_src);
        console.log(js_src);
    }
}
        

Country-Specific Content

The snippets ⁣also demonstrate‌ how to tailor content based on the user’s country. A set_country_flag function dynamically updates‍ elements on the page to display a ​flag⁤ corresponding to the user’s country. This likely relies on a COUNTRY variable defined elsewhere in the ​code.

function set_country_flag(country) {
    country = country.toLowerCase();
    try {
        document.getElementById("show_flag_header").innerHTML = '<div class="flag-icon flag-icon-' + country + ' flag_header"> ';
        document.getElementById("show_flag_header_nav").innerHTML = ' <a href="#country_' + country + '" rel="nofollow noopener"> COUNTRY <div id="flag-nav-frist" class="flag-icon flag-icon-' + country + ' flag-nav-first flag-nav "  >  ';
        document.getElementById("flag_logo").innerHTML = '<div class="flag-icon flag-icon-' + country + ' flag-logo show_flag_logo"  >';
    } catch (err) {}
}
        

The change_country function ⁢redirects the user to a country-specific version‍ of the⁢ website,⁣ updating a cookie to remember the user’s preference.

Lazy Loading‌ Implementation

The code includes a snippet related to “lazysizes,” a popular JavaScript library ⁣for lazy loading images.Lazy loading improves ‌page load times by‌ deferring the loading of images until they ​are about to⁤ enter the viewport.

The provided ⁤snippet appears to be a configuration section for the lazysizes⁣ library, defining ⁣classes and attributes used ​for lazy loading.