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javascript - 在页面加载时获取 localStorage 值

转载 作者：行者123 更新时间：2023-11-30 14:41:05 25 4
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我在网上搜索过，但似乎找不到适合我的东西。

代码如下:

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <title>Heating System Control</title>
        <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
        <script>
        strLED1 = "";
        strLED2 = "";
        strText1 = "";
        strText2 = "";
        var LED1_state = 0;
        var LED2_state = 0;
        function GetArduinoIO()
            {
                nocache = "&nocache=" + Math.random() * 1000000;
                var request = new XMLHttpRequest();
                request.onreadystatechange = function()
                {
                    if (this.readyState == 4) {
                        if (this.status == 200) {
                            if (this.responseXML != null) 
                            {
                            // XML file received - contains analog values, switch values and LED states
                                document.getElementById("input1").innerHTML =
                                    this.responseXML.getElementsByTagName('analog')[0].childNodes[0].nodeValue;
                                document.getElementById("input2").innerHTML =
                                    this.responseXML.getElementsByTagName('analog')[1].childNodes[0].nodeValue;
                                // LED 1
                                if (this.responseXML.getElementsByTagName('LED')[0].childNodes[0].nodeValue === "on") {
                                    document.getElementById("LED1").innerHTML = "ON";
                                    document.getElementById("LED1").style.backgroundColor = "green";
                                    document.getElementById("LED1").style.color = "white";
                                    LED1_state = 1;
                                }
                                else {
                                    document.getElementById("LED1").innerHTML = "OFF";
                                    document.getElementById("LED1").style.backgroundColor = "red";
                                    document.getElementById("LED1").style.color = "white";
                                    LED1_state = 0;
                                }
                                // LED 2
                                if (this.responseXML.getElementsByTagName('LED')[1].childNodes[0].nodeValue === "on") {
                                    document.getElementById("LED2").innerHTML = "ON";
                                    document.getElementById("LED2").style.backgroundColor = "green";
                                    document.getElementById("LED2").style.color = "white";
                                    LED2_state = 1;
                                }
                                else {
                                    document.getElementById("LED2").innerHTML = "OFF";
                                    document.getElementById("LED2").style.backgroundColor = "red";
                                    document.getElementById("LED2").style.color = "white";
                                    LED2_state = 0;
                                }
                            }
                        }
                    }
                }
                // send HTTP GET request with LEDs to switch on/off if any
                request.open("GET", "ajax_inputs" + strLED1 + strLED2 + nocache, true);
                request.send(null);
                setTimeout('GetArduinoIO()', 1000);
                strLED1 = "";
                strLED2 = "";
            }
        function GetButton1()
            {
                if (LED1_state === 1) 
                {
                    LED1_state = 0;
                    strLED1 = "&LED1=0";
                }
                else 
                {
                    LED1_state = 1;
                    strLED1 = "&LED1=1";
                }
            }
        function GetButton2()
            {
                if (LED2_state === 1) 
                {
                    LED2_state = 0;
                    strLED2 = "&LED2=0";
                }
                else 
                {
                    LED2_state = 1;
                    strLED2 = "&LED2=1";
                }
            }
        function SendText1()
            {
                nocache = "&nocache=" + Math.random() * 1000000;
                var request = new XMLHttpRequest();

                strText2 = "&txt2=" + document.getElementById("txt_form1").form_text1.value + "&end2=end";

                request.open("GET", "ajax_inputs" + strText2 + nocache, true);
                request.send(null);
            }
        function SendText2()
            {
                nocache = "&nocache=" + Math.random() * 1000000;
                var request = new XMLHttpRequest();

                strText1 = "&txt1=" + document.getElementById("txt_form2").form_text2.value + "&end1=end";

                request.open("GET", "ajax_inputs" + strText1 + nocache, true);
                request.send(null);
            }
        function clsTxt1()
            {
            setTimeout(
              function clearTxt()
              {
                  document.getElementById("txt_form1").form_text1.value = "";
              }, 500)
            }
        function clsTxt2()
            {
            setTimeout(
              function clearTxt()
              {
                  document.getElementById("txt_form2").form_text2.value = "";
              }, 500)
            }
        function Threshold1()
        {
            var thr1 = document.getElementById("txt_form1").form_text1.value;
            document.getElementById("thresh1").innerHTML = thr1;
        }
        function Threshold2()
            {
                var thr2 = document.getElementById("txt_form2").form_text2.value;
                document.getElementById("thresh2").innerHTML = thr2;
            }
    </script>
    <style>
        .IO_box 
        {
            float: left;
            margin: 0 20px 20px 0;
            border: 1px solid black;
            padding: 0 5px 0 5px;
            width: 100px;
            height: 196px;
            text-align: center;
        }
        h1 
        {
            font-family: Helvetica;
            font-size: 120%;
            color: blue;
            margin: 5px 0 10px 0;
            text-align: center;
        }
        h2 
        {
            font-family: Helvetica;
            font-size: 85%;
            color: black;
            margin: 10px 0 5px 0;
            text-align: center;
        }
        p, form
        {
            font-family: Helvetica;
            font-size: 80%;
            color: #252525;
            text-align: center;
        }
        button
        {
            font-family: Helvetica;
            font-size: 80%;
            max-width: 100px;
            width: 90px;
            height: 25px;
            margin: 0 auto;
            text-align: center;
            border: none;
        }
        input
        {
            font-family: Helvetica;
            font-size: 80%;
            max-width: 100px;
            width: 90px;
            height: 25px;
            margin: 0 auto;
            text-align: center;
            border: none;
        }
        .small_text 
        {
            font-family: Helvetica;
            font-size: 70%;
            color: #737373;
            text-align: center;
        }
        textarea
        {
            resize: none;
            max-width: 90px;
            margin-bottom: 1px;
            text-align: center;
        }
    </style>
    </head>
    <body onload="GetArduinoIO(); Threshold1()">
        <h1>Heating System Control</h1>
        <div class="IO_box">
            <h2>Room One</h2>
            <p>Temp1 is: <span id="input1">...</span></p>
            <button type="button" id="LED1" onclick="GetButton1()" color="white" backgroundColor="red" style="border: none;">OFF</button><br /><br />
            <form id="txt_form1" name="frmText">
                <textarea name="form_text1" rows="1" cols="10"></textarea>
            </form>
            <input type="submit" value="Set Temp" onclick="SendText1(); clsTxt1(); Threshold1();" style ="background-color:#5F9EA0" />
            <p>Threshold: <span id="thresh1">...</span></p>
        </div>
        <div class="IO_box">
            <h2>Room Two</h2>
            <p>Temp2 is: <span id="input2">...</span></p>
            <button type="button" id="LED2" onclick="GetButton2()" color="white" backgroundColor="red" style="border: none;">OFF</button><br /><br />
            <form id="txt_form2" name="frmText">
                <textarea name="form_text2" rows="1" cols="10"></textarea>
            </form>
            <input type="submit" value="Set Temp" onclick="SendText2(); clsTxt2(); Threshold2();" style ="background-color:#5F9EA0" />
            <p>Threshold: <span id="thresh2">...</span></p>
        </div>

    </body>
</html>

所以我的问题是，即使在我重新加载页面(从“Threshold1()”函数)之后，如何保持插入文本区域的值？我找到了一些使用“localStorage”和 JQuery 的示例，但我不知道如何在重新加载页面时调用保存的值。

如有任何帮助，我们将不胜感激。

提前致谢，斯特凡。

最佳答案

本地存储解释

localStorage 对象喜欢存储字符串，那么如何存储大对象，比方说一些复杂的数据结构？ - 很简单，JavaScript 内置了一个简洁的函数，查找 JSON.stringify(object)。所以你需要做的就是像下面这样存储一些复杂的对象，就像我在下面提供的代码一样。然后要从 localStorage 中检索对象，您需要使用 JSON.parse(object);。

要查看 localStorage，我强烈建议您查看 MDN 之类的内容如果你想查看 JSON.parse 和 JSON.stringify 函数，你也可以在这里找到它们:

  1. JSON.parse() link
  2. JSON.stringify() link 

// vanilla js version of $(document).ready(function(){/*code here*/});
window.ready = function(fnc) {
  if (typeof fnc != "function") {
    return console.error("You need to pass a function as a param.");
  }

  try { // try time out for some old IE bugs
    setTimeout(function () {
      document.addEventListener("DOMContentLoaded", fnc());
    }, 10)
  } catch (e) {
    try { // sometimes timeout won't work
      document.addEventListener("DOMContentLoaded", fnc());
    } catch (ex) {
      console.log(ex);
    }
  }
};

// shorter than $(document).ready();
ready(function() {
  var object = {
      name: "Jack",
      age: 30,
      location: "U.S.A.",
      get_pay: function() {
        console.log("test");
      }
    },
    test;

  console.log(object);

  var obj_string = JSON.stringify(object);

  // run a test
  var run_test = function() {
    // output the stored object 
    test = localStorage.getItem("test");
    console.log(test);

    // to make js turn it into an object again 
    test = JSON.parse(localStorage.getItem("test"));
    console.log(test);
  };


  // demo of trying to store an actual object
  try {
    localStorage.setItem("test", object);
    run_test();
  } catch (e) {
    console.log(e);
  }

  // demo of trying to store the string
  try {
    localStorage.setItem("test", obj_string);
    run_test();
  } catch (e) {
    console.log(e);
  }
});

关于javascript - 在页面加载时获取 localStorage 值，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/49653583/

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