如何创建自动完成

学习如何创建自动完成功能。

创建自动完成表单

第一步 - 添加 HTML：

<!-- 确保表单已关闭自动完成功能： -->
<form autocomplete="off" action="/action_page.php">
  <div class="autocomplete" style="width:300px;">
    <input id="myInput" type="text" name="myCountry" placeholder="Country">
  </div>
  <input type="submit">
</form>

第二步 - 创建 JavaScript 数组：

包含世界上所有国家/地区的数组：

var countries = ["Afghanistan","Albania","Algeria","Andorra","Angola","Anguilla","Antigua & Barbuda","Argentina","Armenia","Aruba","Australia","Austria","Azerbaijan","Bahamas","Bahrain","Bangladesh","Barbados","Belarus","Belgium","Belize","Benin","Bermuda","Bhutan","Bolivia","Bosnia & Herzegovina","Botswana","Brazil","British Virgin Islands","Brunei","Bulgaria","Burkina Faso","Burundi","Cambodia","Cameroon","Canada","Cape Verde","Cayman Islands","Central Arfrican Republic","Chad","Chile","China","Colombia","Congo","Cook Islands","Costa Rica","Cote D Ivoire","Croatia","Cuba","Curacao","Cyprus","Czech Republic","Denmark","Djibouti","Dominica","Dominican Republic","Ecuador","Egypt","El Salvador","Equatorial Guinea","Eritrea","Estonia","Ethiopia","Falkland Islands","Faroe Islands","Fiji","Finland","France","French Polynesia","French West Indies","Gabon","Gambia","Georgia","Germany","Ghana","Gibraltar","Greece","Greenland","Grenada","Guam","Guatemala","Guernsey","Guinea","Guinea Bissau","Guyana","Haiti","Honduras","Hong Kong","Hungary","Iceland","India","Indonesia","Iran","Iraq","Ireland","Isle of Man","Israel","Italy","Jamaica","Japan","Jersey","Jordan","Kazakhstan","Kenya","Kiribati","Kosovo","Kuwait","Kyrgyzstan","Laos","Latvia","Lebanon","Lesotho","Liberia","Libya","Liechtenstein","Lithuania","Luxembourg","Macau","Macedonia","Madagascar","Malawi","Malaysia","Maldives","Mali","Malta","Marshall Islands","Mauritania","Mauritius","Mexico","Micronesia","Moldova","Monaco","Mongolia","Montenegro","Montserrat","Morocco","Mozambique","Myanmar","Namibia","Nauro","Nepal","Netherlands","Netherlands Antilles","New Caledonia","New Zealand","Nicaragua","Niger","Nigeria","North Korea","Norway","Oman","Pakistan","Palau","Palestine","Panama","Papua New Guinea","Paraguay","Peru","Philippines","Poland","Portugal","Puerto Rico","Qatar","Reunion","Romania","Russia","Rwanda","Saint Pierre & Miquelon","Samoa","San Marino","Sao Tome and Principe","Saudi Arabia","Senegal","Serbia","Seychelles","Sierra Leone","Singapore","Slovakia","Slovenia","Solomon Islands","Somalia","South Africa","South Korea","South Sudan","Spain","Sri Lanka","St Kitts & Nevis","St Lucia","St Vincent","Sudan","Suriname","Swaziland","Sweden","Switzerland","Syria","Taiwan","Tajikistan","Tanzania","Thailand","Timor L'Este","Togo","Tonga","Trinidad & Tobago","Tunisia","Turkey","Turkmenistan","Turks & Caicos","Tuvalu","Uganda","Ukraine","United Arab Emirates","United Kingdom","United States of America","Uruguay","Uzbekistan","Vanuatu","Vatican City","Venezuela","Vietnam","Virgin Islands (US)","Yemen","Zambia","Zimbabwe"];

第三步 - 添加 CSS：

容器必须具有“相对”定位。

* { box-sizing: border-box; }
body {
  font: 16px Arial;
}
.autocomplete {
  /*容器必须相对定位： */
  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;
}
.autocomplete-items {
  position: absolute;
  border: 1px solid #d4d4d4;
  border-bottom: none;
  border-top: none;
  z-index: 99;
  /* 将自动完成项定位为与容器相同的宽度： */
  top: 100%;
  left: 0;
  right: 0;
}
.autocomplete-items div {
  padding: 10px;
  cursor: pointer;
  background-color: #fff;
  border-bottom: 1px solid #d4d4d4;
}
.autocomplete-items div:hover {
  /* 当鼠标悬停在项目上时： */
  background-color: #e9e9e9;
}
.autocomplete-active {
  /* 当使用箭头键浏览项目时：*/
  background-color: DodgerBlue !important;
  color: #ffffff;
}

第四步 - 添加 JavaScript：

function autocomplete(inp, arr) {
  /* 自动完成函数需要两个参数，一个是文本字段元素，另一个是可以自动完成的可能值的数组： */
  var currentFocus;
  /* 当有人在文本字段中写入时执行的函数： */
  inp.addEventListener("input", function(e) {
      var a, b, i, val = this.value;
      /* 关闭任何已经打开的自动完成值列表 */
      closeAllLists();
      if (!val) { return false;}
      currentFocus = -1;
      /* 创建一个包含项目（值）的 DIV 元素： */
      a = document.createElement("DIV");
      a.setAttribute("id", this.id + "autocomplete-list");
      a.setAttribute("class", "autocomplete-items");
      /* 将这个 DIV 元素附加为自动完成容器的子元素：*/
      this.parentNode.appendChild(a);
      /* 遍历数组中的每个项目... */
      for (i = 0; i < arr.length; i++) {
        /* 检查项目是否以与文本字段值相同的字母开头： */
        if (arr[i].substr(0, val.length).toUpperCase() == val.toUpperCase()) {
          /* 为每个匹配元素创建一个 DIV 元素： */
          b = document.createElement("DIV");
          /* 将匹配的字母加粗： */
          b.innerHTML = "<strong>" + arr[i].substr(0, val.length) + "</strong>";
          b.innerHTML += arr[i].substr(val.length);
          /* 插入一个输入字段来保存当前数组项的值： */
          b.innerHTML += "<input type='hidden' value='" + arr[i] + "'>";
          /* 当有人单击项目值（DIV 元素）时执行的函数： */
              b.addEventListener("click", function(e) {
              /* 插入自动完成文本字段的值： */
              inp.value = this.getElementsByTagName("input")[0].value;
              /*关闭自动完成值列表，或任何其他打开的自动完成值列表： */
              closeAllLists();
          });
          a.appendChild(b);
        }
      }
  });
  /* 当有人在键盘上按键时执行一个函数：*/
  inp.addEventListener("keydown", function(e) {
      var x = document.getElementById(this.id + "autocomplete-list");
      if (x) x = x.getElementsByTagName("div");
      if (e.keyCode == 40) {
        /*如果按下箭头向下键，增加 currentFocus 变量：*/
        currentFocus++;
        /* 并使当前项目更加明显：*/
        addActive(x);
      } else if (e.keyCode == 38) { //up
        /* 如果按下向上箭头键，减少 currentFocus 变量：*/
        currentFocus--;
        /* 并使当前项目更加明显：*/
        addActive(x);
      } else if (e.keyCode == 13) {
        /* 如果按下 ENTER 键，则阻止提交表单：*/
        e.preventDefault();
        if (currentFocus > -1) {
          /* 并模拟点击“活动”项目：*/
          if (x) x[currentFocus].click();
        }
      }
  });
  function addActive(x) {
    /* 将项目分类为“活动”的函数：*/
    if (!x) return false;
    /* 首先删除所有项目中的 "active" 类：*/
    removeActive(x);
    if (currentFocus >= x.length) currentFocus = 0;
    if (currentFocus < 0) currentFocus = (x.length - 1);
    /* 添加 "autocomplete-active" 类：*/
    x[currentFocus].classList.add("autocomplete-active");
  }
  function removeActive(x) {
    /* 从所有自动完成项中删除 "active" 类的函数：*/
    for (var i = 0; i < x.length; i++) {
      x[i].classList.remove("autocomplete-active");
    }
  }
  function closeAllLists(elmnt) {
    /*关闭文档中的所有自动完成列表，除了作为参数传递的那个：*/
    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]);
    }
  }
}
/* 当有人单击文档时执行的函数*/
document.addEventListener("click", function (e) {
    closeAllLists(e.target);
});
}

第五步 - 在 "myInput" 上启用自动完成功能：

将国家数组作为 autocomplete 函数的第二个参数传递：

<script>
autocomplete(document.getElementById("myInput"), countries);
</script>

亲自试一试