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javascript - 将用户输入限制为预定义的值列表

问题描述

我有一个input带有 id 的标签，myInput可以让用户输入值。我还有一个自动完成功能，它由一个countries使用预填充值调用的数组支持。

我希望用户只能提交与预填充列表匹配的值。

例如，我有一个具有以下值的数组->['USA','CHINA','RUSSIA'];

因此，我不希望用户输入一些随机输入，例如“abc”或“xyz”，我只希望他们能够提交与我的列表匹配的输入。这可能吗？

我的 HTML 代码

 <div class="container">
 <div class="autocomplete" style="width:300px;">
    <input id="myInput" type="text" name="myCountry" placeholder="Country">
  </div>
  <input type="submit" onclick="getInput()">
 </div>

我的 JS 代码

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 = ['USA','CHINA','RUSSIA'];
    autocomplete(document.getElementById("myInput"), countries);





function getInput(){
  alert(document.getElementById('myInput').value);
}

我的小提琴

自动完成代码取自w3schools

标签： javascripthtml

解决方案

你可以试试<datalist>HTML 的标签，见https://www.w3schools.com/tags/tag_datalist.asp

更新后的 HTML 代码：

<div class="container">

    <div class="autocomplete" style="width:300px;">
        <input id="myInput" type="text" name="myCountry" list="Country">
        <datalist id="Country">
            <option value="USA">
            <option value="CHINA">
            <option value="RUSSIA">
        </datalist>
    </div>
    <input type="submit" onclick="getInput()">
</div>

<datalist>可以使用 javascript 动态更改的内容：

// dynamically fill the available text input options
var countries = ['a', 'ab', 'abc'];
var objTable = document.getElementById("Country");
objTable.innerHTML += "<option>" + countries[0] + "</option>";
objTable.innerHTML += "<option>" + countries[1] + "</option>";
objTable.innerHTML += "<option>" + countries[2] + "</option>";

关于用户输入限制：可以用javascript验证用户输入，然后根据输入有效性选择继续或放弃。

如果您想使用纯 HTML 限制用户输入，请考虑使用<select>标签，它将用户的输入限制在一定范围内，同时在按键时仍提供用户友好的“半自动完成”：https://www .w3schools.com/tags/tag_select.asp

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