document.querySelector 跳過不存在的元素

Question

我正在使用它在頁面中添加廣告，我在頁面上有大約 5 個廣告，每個廣告都放入不同的元素中。 我遇到的問題是在某些頁面上所有元素都不存在，所以如果它們不存在，我想“跳過”它們，此時它找到第一個元素，添加廣告，如果下一個頁面上沒有元素，它會出錯，然后不會在以下元素中顯示廣告。 希望這是有道理的？

這個元素在某個頁面上，但不在其他頁面上，所以我怎么能在它不存在的頁面上“跳過它”

document.querySelector("#spacer1").insertAdjacentHTML('afterbegin',........

完整代碼使用：

//shows the slots on the page
window.addEventListener("DOMContentLoaded", function() {
  document.querySelector(".p-body-inner").insertAdjacentHTML('afterbegin', '<div class="ad-reporter-ahytrfg35423"><div id="advertisement" style="border: 0pt none; margin: auto; text-align: center; color: #999; text-transform: uppercase; font-family: sans-serif; font-size: 9px; font-weight: 400; letter-spacing: .2em; line-height: 1; margin-top: 0px; position: relative; top: -4px;">Advertisement</div><div id="inreedvid13Slot"></div></div><br>');
  document.querySelector("#spacer1").insertAdjacentHTML('afterbegin', '<div class="ad-reporter-ahytrfg35423"><div id="advertisement" style="border: 0pt none; margin: auto; text-align: center; color: #999; text-transform: uppercase; font-family: sans-serif; font-size: 9px; font-weight: 400; letter-spacing: .2em; line-height: 1; margin-top: 0px; position: relative; top: -4px;">Advertisement</div><div id="inreedvid9Slot"></div></div><br><br><br>');
  document.querySelector(".block.block--category.block--category99").insertAdjacentHTML('beforeend', '<br><div class="ad-reporter-ahytrfg35423"><div id="advertisement" style="border: 0pt none; margin: auto; text-align: center; color: #999; text-transform: uppercase; font-family: sans-serif; font-size: 9px; font-weight: 400; letter-spacing: .2em; line-height: 1; margin-top: 0px; position: relative; top: -4px;">Advertisement</div><div id="inreedvid8Slot"></div></div>');
  document.querySelector("#spacer2").insertAdjacentHTML('beforebegin', '<br><div class="ad-reporter-ahytrfg35423"><div id="advertisement" style="border: 0pt none; margin: auto; text-align: center; color: #999; text-transform: uppercase; font-family: sans-serif; font-size: 9px; font-weight: 400; letter-spacing: .2em; line-height: 1; margin-top: 0px; position: relative; top: -4px;">Advertisement</div><div id="inreedvid5Slot"></div></div><br>');
  document.querySelector(".p-breadcrumbs.p-breadcrumbs--bottom").insertAdjacentHTML('afterend', '<br><div class="ad-reporter-ahytrfg35423"><div id="advertisement" style="border: 0pt none; margin: auto; text-align: center; color: #999; text-transform: uppercase; font-family: sans-serif; font-size: 9px; font-weight: 400; letter-spacing: .2em; line-height: 1; margin-top: 0px; position: relative; top: -4px;">Advertisement</div><div id="inreedvid4Slot"></div></div><br>');
  document.querySelector("#adfooter").insertAdjacentHTML('afterbegin', '<br><div class="ad-reporter-ahytrfg35423"><div id="advertisement" style="border: 0pt none; margin: auto; text-align: center; color: #999; text-transform: uppercase; font-family: sans-serif; font-size: 9px; font-weight: 400; letter-spacing: .2em; line-height: 1; margin-top: 0px; position: relative; top: -4px;">Advertisement</div><div id="inreedvid6Slot"></div></div><br>');
});

因此，由於以下答案，上述工作現在有效，非常感謝：下一個問題是它現在給出錯誤，因為我的預投標文件正試圖將“插槽”放置在 div 插槽由於有用的答案而被排除/跳過的頁面上，所以我認為我需要一些邏輯，以在已排除插槽 div 時停止將插槽發送到頁面？ 這是從 prebid 文件發送槽的代碼：

(window.googletag, window.pbjs, {
definitons: {
inreedvid13Slot: { adUnitPath: "/slotnumber/slotname", size: [[970, 90],[970, 250],[728, 90],[468, 60],[320, 50],[320, 100]], sizeMapping: "mappingleaderslot", timeout: site_config.refresh_rate, },
inreedvid9Slot: { adUnitPath: "/slotnumber/slotname", size: [[300, 600],[300, 250],[250, 250],[160, 600],[120, 600]], sizeMapping: "mappingmenuslot", timeout: site_config.refresh_rate, },
inreedvid5Slot: { adUnitPath: "/slotnumber/slotname", size: [[300, 600],[300, 250],[250, 250],[160, 600],[120, 600]], sizeMapping: "mappingmenuslot", timeout: site_config.refresh_rate, },
inreedvid8Slot: { adUnitPath: "/slotnumber/slotname", size: [[550, 310],[728, 90],[300, 250],[250, 250],[468, 60],[320, 50],[336, 280],[580, 400],[320, 100]], sizeMapping: "mappinginreedvidslot", timeout: site_config.refresh_rate, },
inreedvid4Slot: { adUnitPath: "/slotnumber/slotname", size: [[550, 310],[728, 90],[300, 250],[250, 250],[468, 60],[320, 50],[336, 280],[580, 400],[320, 100]], sizeMapping: "mappinginreedvidslot", timeout: site_config.refresh_rate, },
inreedvid7Slot: { adUnitPath: "/slotnumber/slotname", size: [[550, 310],[728, 90],[300, 250],[250, 250],[468, 60],[320, 50],[336, 280],[580, 400],[320, 100]], sizeMapping: "mappinginreedvidslot", timeout: site_config.refresh_rate, },
inreedvid10Slot: { adUnitPath: "/slotnumber/slotname", size: [[550, 310],[970, 250],[970, 90],[728, 90],[300, 250],[250, 250],[468, 60],[320, 50],[336, 280],[580, 400],[320, 100]], sizeMapping: "mappinginreedvidslot", timeout: site_config.refresh_rate, },
inreedvid6Slot: { adUnitPath: "/slotnumber/slotname", size: [[970, 90],[728, 90],[468, 60],[320, 50],[320, 100]], sizeMapping: "mappingfooterslot", timeout: site_config.refresh_rate, },
},

我可以在其中添加一個 querySelector，因為當 div 在頁面上生成取決於哪些元素存在時，有一個 div class="ad-reporter-ahytrfg35423">，所以我可以使用它來確定哪個“插槽”開火？

Answer 1

在嘗試訪問之前，您需要確保 querySelector 調用返回一些內容。

為此，您需要添加一個條件。

您還可以使用數組來幫助使此過程在代碼方面更加優雅。

例如：

 //shows the slots on the page window.addEventListener("DOMContentLoaded", function() { const ads = [ { "selector": ".p-body-inner", "location": "afterbegin", "html": '<div class="ad-reporter-ahytrfg35423"><div id="advertisement" style="border: 0pt none; margin: auto; text-align: center; color: #999; text-transform: uppercase; font-family: sans-serif; font-size: 9px; font-weight: 400; letter-spacing: .2em; line-height: 1; margin-top: 0px; position: relative; top: -4px;">Advertisement</div><div id="inreedvid13Slot"></div></div><br>', }, // This selector doesn't exist in this snippet and will be skipped by the condition below without crashing... { "selector": "#spacer1", "location": "afterbegin", "html": '<div class="ad-reporter-ahytrfg35423"><div id="advertisement" style="border: 0pt none; margin: auto; text-align: center; color: #999; text-transform: uppercase; font-family: sans-serif; font-size: 9px; font-weight: 400; letter-spacing: .2em; line-height: 1; margin-top: 0px; position: relative; top: -4px;">Advertisement</div><div id="inreedvid9Slot"></div></div><br><br><br>', }, // Add your other ads here using similar structure above... ]; ads.forEach(ad => { adContainer = document.querySelector(ad.selector); if (adContainer) { adContainer.insertAdjacentHTML(ad.location, ad.html); } }); });

 <div class="p-body-inner"></div>