如何自动聚焦列表的第一个元素

Question

我想始终将currentFocus放在第一个元素上。 现在您必须使用向下按钮在第一个元素上显示currentFocus 。 我希望它始终专注于第一个元素。 实现这一点的最佳方法是什么？ 我要操作的代码来自 w3schools。

示例数据：["阿富汗"、"阿尔巴尼亚"、"阿尔及利亚"]

 function autocomplete(inp, arr) { /*the autocomplete function takes two arguments, the text field element and an array of possible autocompleted values:*/ var currentFocus; /*execute a function when someone writes in the text field:*/ inp.addEventListener("input", function(e) { var a, b, i, val = this.value; /*close any already open lists of autocompleted values*/ closeAllLists(); if (!val) { return false;} currentFocus = -1; /*create a DIV element that will contain the items (values):*/ a = document.createElement("DIV"); a.setAttribute("id", this.id + "autocomplete-list"); a.setAttribute("class", "autocomplete-items"); /*append the DIV element as a child of the autocomplete container:*/ this.parentNode.appendChild(a); /*for each item in the array...*/ for (i = 0; i < arr.length; i++) { /*check if the item starts with the same letters as the text field value:*/ if (arr[i].substr(0, val.length).toUpperCase() == val.toUpperCase()) { /*create a DIV element for each matching element:*/ b = document.createElement("DIV"); /*make the matching letters bold:*/ b.innerHTML = "<strong>" + arr[i].substr(0, val.length) + "</strong>"; b.innerHTML += arr[i].substr(val.length); /*insert a input field that will hold the current array item's value:*/ b.innerHTML += "<input type='hidden' value='" + arr[i] + "'>"; /*execute a function when someone clicks on the item value (DIV element):*/ b.addEventListener("click", function(e) { /*insert the value for the autocomplete text field:*/ inp.value = this.getElementsByTagName("input")[0].value; /*close the list of autocompleted values, (or any other open lists of autocompleted values:*/ closeAllLists(); }); a.appendChild(b); } } }); /*execute a function presses a key on the keyboard:*/ inp.addEventListener("keydown", function(e) { var x = document.getElementById(this.id + "autocomplete-list"); if (x) x = x.getElementsByTagName("div"); if (e.keyCode == 40) { /*If the arrow DOWN key is pressed, increase the currentFocus variable:*/ currentFocus++; /*and and make the current item more visible:*/ addActive(x); } else if (e.keyCode == 38) { //up /*If the arrow UP key is pressed, decrease the currentFocus variable:*/ currentFocus--; /*and and make the current item more visible:*/ addActive(x); } else if (e.keyCode == 13) { /*If the ENTER key is pressed, prevent the form from being submitted,*/ e.preventDefault(); if (currentFocus > -1) { /*and simulate a click on the "active" item:*/ if (x) x[currentFocus].click(); } } }); function addActive(x) { /*a function to classify an item as "active":*/ if (!x) return false; /*start by removing the "active" class on all items:*/ removeActive(x); if (currentFocus >= x.length) currentFocus = 0; if (currentFocus < 0) currentFocus = (x.length - 1); /*add class "autocomplete-active":*/ x[currentFocus].classList.add("autocomplete-active"); } function removeActive(x) { /*a function to remove the "active" class from all autocomplete items:*/ for (var i = 0; i < x.length; i++) { x[i].classList.remove("autocomplete-active"); } } function closeAllLists(elmnt) { /*close all autocomplete lists in the document, except the one passed as an argument:*/ var x = document.getElementsByClassName("autocomplete-items"); for (var i = 0; i < x.length; i++) { if (elmnt != x[i] && elmnt != inp) { x[i].parentNode.removeChild(x[i]); } } } /*execute a function when someone clicks in the document:*/ document.addEventListener("click", function (e) { closeAllLists(e.target); }); } var countries = ["Afghanistan","Albania","Algeria"] /*initiate the autocomplete function on the "myInput" element, and pass along the countries array as possible autocomplete values:*/ autocomplete(document.getElementById("myInput"), countries);

 * { box-sizing: border-box; } body { font: 16px Arial; } /*the container must be positioned relative:*/ .autocomplete { position: relative; display: inline-block; } input { border: 1px solid transparent; background-color: #f1f1f1; padding: 10px; font-size: 16px; } input[type=text] { background-color: #f1f1f1; width: 100%; } input[type=submit] { background-color: DodgerBlue; color: #fff; cursor: pointer; } .autocomplete-items { position: absolute; border: 1px solid #d4d4d4; border-bottom: none; border-top: none; z-index: 99; /*position the autocomplete items to be the same width as the container:*/ top: 100%; left: 0; right: 0; } .autocomplete-items div { padding: 10px; cursor: pointer; background-color: #fff; border-bottom: 1px solid #d4d4d4; } /*when hovering an item:*/ .autocomplete-items div:hover { background-color: #e9e9e9; } /*when navigating through the items using the arrow keys:*/ .autocomplete-active { background-color: DodgerBlue !important; color: #ffffff; }

 <h2>Autocomplete</h2> <p>Start typing:</p> <!--Make sure the form has the autocomplete function switched off:--> <form autocomplete="off" action="/action_page.php"> <div class="autocomplete" style="width:300px;"> <input id="myInput" type="text" name="myCountry" placeholder="Country"> </div> </form>

Answer 1

您缺少的是设置默认选择的第一个搜索结果。 在将项目与输入匹配的循环中添加以下代码，它将像魅力一样工作。

if (currentFocus === -1) {
    currentFocus = 0;
    b.classList.add("autocomplete-active");
}

 function autocomplete(inp, arr) { /*the autocomplete function takes two arguments, the text field element and an array of possible autocompleted values:*/ var currentFocus; /*execute a function when someone writes in the text field:*/ inp.addEventListener("input", function(e) { var a, b, i, val = this.value; /*close any already open lists of autocompleted values*/ closeAllLists(); if (!val) { return false;} currentFocus = -1; /*create a DIV element that will contain the items (values):*/ a = document.createElement("DIV"); a.setAttribute("id", this.id + "autocomplete-list"); a.setAttribute("class", "autocomplete-items"); /*append the DIV element as a child of the autocomplete container:*/ this.parentNode.appendChild(a); /*for each item in the array...*/ for (i = 0; i < arr.length; i++) { /*check if the item starts with the same letters as the text field value:*/ if (arr[i].substr(0, val.length).toUpperCase() == val.toUpperCase()) { /*create a DIV element for each matching element:*/ b = document.createElement("DIV"); if (currentFocus === -1) { currentFocus = 0; b.classList.add("autocomplete-active"); } /*make the matching letters bold:*/ b.innerHTML = "<strong>" + arr[i].substr(0, val.length) + "</strong>"; b.innerHTML += arr[i].substr(val.length); /*insert a input field that will hold the current array item's value:*/ b.innerHTML += "<input type='hidden' value='" + arr[i] + "'>"; /*execute a function when someone clicks on the item value (DIV element):*/ b.addEventListener("click", function(e) { /*insert the value for the autocomplete text field:*/ inp.value = this.getElementsByTagName("input")[0].value; /*close the list of autocompleted values, (or any other open lists of autocompleted values:*/ closeAllLists(); }); a.appendChild(b); } } }); /*execute a function presses a key on the keyboard:*/ inp.addEventListener("keydown", function(e) { var x = document.getElementById(this.id + "autocomplete-list"); if (x) x = x.getElementsByTagName("div"); if (e.keyCode == 40) { /*If the arrow DOWN key is pressed, increase the currentFocus variable:*/ currentFocus++; /*and and make the current item more visible:*/ addActive(x); } else if (e.keyCode == 38) { //up /*If the arrow UP key is pressed, decrease the currentFocus variable:*/ currentFocus--; /*and and make the current item more visible:*/ addActive(x); } else if (e.keyCode == 13) { /*If the ENTER key is pressed, prevent the form from being submitted,*/ e.preventDefault(); if (currentFocus > -1) { /*and simulate a click on the "active" item:*/ if (x) x[currentFocus].click(); } } }); function addActive(x) { /*a function to classify an item as "active":*/ if (!x) return false; /*start by removing the "active" class on all items:*/ removeActive(x); if (currentFocus >= x.length) currentFocus = 0; if (currentFocus < 0) currentFocus = (x.length - 1); /*add class "autocomplete-active":*/ x[currentFocus].classList.add("autocomplete-active"); } function removeActive(x) { /*a function to remove the "active" class from all autocomplete items:*/ for (var i = 0; i < x.length; i++) { x[i].classList.remove("autocomplete-active"); } } function closeAllLists(elmnt) { /*close all autocomplete lists in the document, except the one passed as an argument:*/ var x = document.getElementsByClassName("autocomplete-items"); for (var i = 0; i < x.length; i++) { if (elmnt != x[i] && elmnt != inp) { x[i].parentNode.removeChild(x[i]); } } } /*execute a function when someone clicks in the document:*/ document.addEventListener("click", function (e) { closeAllLists(e.target); }); } var countries = ["Afghanistan","Albania","Algeria"] /*initiate the autocomplete function on the "myInput" element, and pass along the countries array as possible autocomplete values:*/ autocomplete(document.getElementById("myInput"), countries);

 * { box-sizing: border-box; } body { font: 16px Arial; } /*the container must be positioned relative:*/ .autocomplete { position: relative; display: inline-block; } input { border: 1px solid transparent; background-color: #f1f1f1; padding: 10px; font-size: 16px; } input[type=text] { background-color: #f1f1f1; width: 100%; } input[type=submit] { background-color: DodgerBlue; color: #fff; cursor: pointer; } .autocomplete-items { position: absolute; border: 1px solid #d4d4d4; border-bottom: none; border-top: none; z-index: 99; /*position the autocomplete items to be the same width as the container:*/ top: 100%; left: 0; right: 0; } .autocomplete-items div { padding: 10px; cursor: pointer; background-color: #fff; border-bottom: 1px solid #d4d4d4; } /*when hovering an item:*/ .autocomplete-items div:hover { background-color: #e9e9e9; } /*when navigating through the items using the arrow keys:*/ .autocomplete-active { background-color: DodgerBlue !important; color: #ffffff; }

 <h2>Autocomplete</h2> <p>Start typing:</p> <!--Make sure the form has the autocomplete function switched off:--> <form autocomplete="off" action="/action_page.php"> <div class="autocomplete" style="width:300px;"> <input id="myInput" type="text" name="myCountry" placeholder="Country"> </div> </form>