無法使用getElementById

Question

無法使用getElementById（「VAL5」+ i）。 然後輸入3不運行

我用這個代碼足夠的信息希望能提供

錯誤是某處線

/* DigitalInput */

指數= input2_offs 爲（i = 0; i < 4; i ++） getElementById（「VAL5」+ i）.src = valueArray [input2_offs [i]] ==「0」？ 'GIF/dot_red.gif'： 'GIF/dot_gr.gif'

哪裏出了問題

---

enter code here 

<!-- 

var req = null; 
req = AjaxInit(); 
var PostBuffer = new Array; 

var Trace; 

/* number of channels per sensor input type */ 
var InputChannels = 4; /* max 4 digital inputs   */ 

var names = new Array(); 
var units = new Array(); 
var offs = new Array(); 
var gain = new Array(); 
var value = new Array(); 

var input2_offs = 25; 
var input3_offs = 26; 

/* 
    this function is called on body load and later every 5s 
    request a new set of data from the controller 
*/ 
function UpDate() 
{ 
    var x = Math.random()*1000; /* add random number to the url to avoid caching the content in the browser */ 
    x=x.toFixed(3); 
    AjaxGetRequest("/GetState.csv"+"?a="+x,UpdateTraceBuffers); 
    return false; 
} 

/* 
    call back routine when the controller has send the data 
    this function separates all items in separate arrays as : 
    names, units, offsets , gains and the raw values 
*/ 
function UpdateTraceBuffers() 
{ 

    Trace = req.responseText.split('\n'); 
    names = Trace[TraceNameOffs].split(','); 
    units = Trace[TraceUnitOffs].split(','); 
    offs = Trace[TraceOffs].split(','); 
    gain = Trace[TraceGain].split(','); 
    value = Trace[TraceDataoffs].split(','); 
    UpdateWebSite();       /* user routine , update all items */ 
    if(timerHandle == 0) 
    { 
     timerHandle = window.setInterval("UpDate()", 5000); 
    } 
} 

/* DigitalInput */ 

    index = input2_offs; 
      for(i=0;i<4;i++) 
    getElementById("VAL5"+i).src = valueArray[input2_offs[i]] == "0" ? 'gif/dot_red.gif' : 'gif/dot_gr.gif'; 

    index = input3_offs; 
    v = (parseFloat(offs[index]) + parseFloat(gain[index])* parseFloat(value[index])).toFixed(0); 
      getElementById("SENS_VAL6").innerHTML = v; 

//--> 


<td class="mytd"><div align="center"><img src="gif/dot_red.gif" 
width="24" height="24" id="VAL5"></div></td> 
<td id="SENS_VAL6" class="mytd" align="right">&nbsp;</td> 

Answer 1

document.getElementById("VAL5"+i); 

或者你可以使用：

document.querySelector （「VAL5」+ i）

適用於所有現代瀏覽器（IE8 +）。 https://developer.mozilla.org/en-US/docs/Web/API/document.querySelector

實際上在for循環中使用{}，if語句等等，這是js中的推薦做法。