javascript - 为什么 JavaScript 控制台说我的变量未定义，即使我在两行之前定义了它？

Question

我正在使用 WebSockets 连接到远程主机，每当我填充 realData 并将其传递给 grapher() 时，JavaScript 控制台一直告诉我 realData 未定义。我尝试检查数组中数据的类型，但似乎没问题。在使用带有随机数据的数组之前，我调用了 grapher()，并且调用没有任何问题。然而，对于来自 WebSocket 的数据，调用总是会给我“错误:未定义 realData”。我不确定为什么会这样。这是我使用的代码:

current.html:

var command = "Hi Scott"

getData();

function getData()
 { 
    console.log("getData is called");

    if("WebSocket" in window)
    {
            var dataCollector = new WebSocket("ws://console.sb2.orbit-lab.org:6100",'binary');
            dataCollector.binaryType = "arraybuffer";
            console.log(dataCollector.readyState);        

            dataCollector.onopen = function()
            {
                    //alert("The WebSocket is now open!");                  

                    console.log("Ready state in onopen is: " + dataCollector.readyState);


                    dataCollector.send(command);
                    console.log(command + " sent"); 
            }

            dataCollector.onmessage = function(evt)
            {


                            console.log("onmessage is being called");
                            var realData = new Uint8Array(evt.data);
                            console.log(realData);
                            grapher(realData); //everything up to this point works perfectly.
            }

            dataCollector.onclose = function()
            {
                    alert("Connection to Server has been closed");
            }


            return (dataCollector);
    }
    else
    {
            alert("Your browser does not support WebSockets!");
    }

绘图.js:

function grapher(realData)
{
            console.log("grapher is called");
            setInterval('myGraph(realData);',1000); //This is where the error is. I always get "realData is not defined".

}

function myGraph(realData)
{
            /*
           for(var i = 0; i < SAarray.length; i++) // Loop which will load the channel data from the SA objects into the data array for graphing.
            {
                    var data[i] = SAarray[i];
            }
            */
            console.log("myGraph is called");

            var bar = new RGraph.Bar('channelStatus', realData);
            bar.Set('labels', ['1','2','3','4','5','6','7','8']);
            bar.Set('gutter.left', 50);
            bar.Set('gutter.bottom', 40);
            bar.Set('ymax',100);
            bar.Set('ymin',0);
            bar.Set('scale.decimals',1);
            bar.Set('title','Channel Status');
            bar.Set('title.yaxis','Status (1 is on, 0 is off)');
            bar.Set('title.xaxis','Channel Number');
            bar.Set('title.xaxis.pos',.1);
            bar.Set('background.color','white');
            bar.Set('colors', ['Gradient(#a33:red)']);
            bar.Set('colors', ['red']);

            bar.Set('key',['Occupied','Unoccupied']);

            bar.getShapeByX(2).Set('colors',barColor(data[0]));


            bar.Draw();


}

Answer 1

因为传递给 setInterval 的字符串(作为代码)在全局范围内执行，因此 realData 参数不可用。很少有充分的理由将字符串传递给 setInterval。相反，使用:

setInterval(function () {
    myGraph(realData);
}, 1000);

引用:

• https://developer.mozilla.org/en-US/docs/Web/API/window.setInterval