如何創建自動完成

學習如何創建自動完成功能。

創建自動完成表單

第一步 - 添加 HTML：

<!-- 確保表單已關閉自動完成功能： -->
<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 - 創建 JavaScript 數組：

包含世界上所有國家/地區的數組：

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：

容器必須具有“相對”定位。

* { box-sizing: border-box; }
body {
  font: 16px Arial;
}
.autocomplete {
  /*容器必須相對定位： */
  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;
  /* 將自動完成項定位為與容器相同的寬度： */
  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 {
  /* 當鼠標懸停在項目上時： */
  background-color: #e9e9e9;
}
.autocomplete-active {
  /* 當使用箭頭鍵瀏覽項目時：*/
  background-color: DodgerBlue !important;
  color: #ffffff;
}

第四步 - 添加 JavaScript：

function autocomplete(inp, arr) {
  /* 自動完成函數需要兩個參數，一個是文本字段元素，另一個是可以自動完成的可能值的數組： */
  var currentFocus;
  /* 當有人在文本字段中寫入時執行的函數： */
  inp.addEventListener("input", function(e) {
      var a, b, i, val = this.value;
      /* 關閉任何已經打開的自動完成值列表 */
      closeAllLists();
      if (!val) { return false;}
      currentFocus = -1;
      /* 創建一個包含項目（值）的 DIV 元素： */
      a = document.createElement("DIV");
      a.setAttribute("id", this.id + "autocomplete-list");
      a.setAttribute("class", "autocomplete-items");
      /* 將這個 DIV 元素附加為自動完成容器的子元素：*/
      this.parentNode.appendChild(a);
      /* 遍歷數組中的每個項目... */
      for (i = 0; i < arr.length; i++) {
        /* 檢查項目是否以與文本字段值相同的字母開頭： */
        if (arr[i].substr(0, val.length).toUpperCase() == val.toUpperCase()) {
          /* 為每個匹配元素創建一個 DIV 元素： */
          b = document.createElement("DIV");
          /* 將匹配的字母加粗： */
          b.innerHTML = "<strong>" + arr[i].substr(0, val.length) + "</strong>";
          b.innerHTML += arr[i].substr(val.length);
          /* 插入一個輸入字段來保存當前數組項的值： */
          b.innerHTML += "<input type='hidden' value='" + arr[i] + "'>";
          /* 當有人單擊項目值（DIV 元素）時執行的函數： */
              b.addEventListener("click", function(e) {
              /* 插入自動完成文本字段的值： */
              inp.value = this.getElementsByTagName("input")[0].value;
              /*關閉自動完成值列表，或任何其他打開的自動完成值列表： */
              closeAllLists();
          });
          a.appendChild(b);
        }
      }
  });
  /* 當有人在鍵盤上按鍵時執行一個函數：*/
  inp.addEventListener("keydown", function(e) {
      var x = document.getElementById(this.id + "autocomplete-list");
      if (x) x = x.getElementsByTagName("div");
      if (e.keyCode == 40) {
        /*如果按下箭頭向下鍵，增加 currentFocus 變量：*/
        currentFocus++;
        /* 并使當前項目更加明顯：*/
        addActive(x);
      } else if (e.keyCode == 38) { //up
        /* 如果按下向上箭頭鍵，減少 currentFocus 變量：*/
        currentFocus--;
        /* 并使當前項目更加明顯：*/
        addActive(x);
      } else if (e.keyCode == 13) {
        /* 如果按下 ENTER 鍵，則阻止提交表單：*/
        e.preventDefault();
        if (currentFocus > -1) {
          /* 并模擬點擊“活動”項目：*/
          if (x) x[currentFocus].click();
        }
      }
  });
  function addActive(x) {
    /* 將項目分類為“活動”的函數：*/
    if (!x) return false;
    /* 首先刪除所有項目中的 "active" 類：*/
    removeActive(x);
    if (currentFocus >= x.length) currentFocus = 0;
    if (currentFocus < 0) currentFocus = (x.length - 1);
    /* 添加 "autocomplete-active" 類：*/
    x[currentFocus].classList.add("autocomplete-active");
  }
  function removeActive(x) {
    /* 從所有自動完成項中刪除 "active" 類的函數：*/
    for (var i = 0; i < x.length; i++) {
      x[i].classList.remove("autocomplete-active");
    }
  }
  function closeAllLists(elmnt) {
    /*關閉文檔中的所有自動完成列表，除了作為參數傳遞的那個：*/
    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]);
    }
  }
}
/* 當有人單擊文檔時執行的函數*/
document.addEventListener("click", function (e) {
    closeAllLists(e.target);
});
}

第五步 - 在 "myInput" 上啟用自動完成功能：

將國家數組作為 autocomplete 函數的第二個參數傳遞：

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

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