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Question

此代碼提醒'測試1'，然後提醒8！

uri = 'http://www.scriptcopy.com/'; 
compareuris = new Array(); 
compareuris[0] = 'http://www.scriptcopy.com/'; 
compareuris[1] = 'https://www.scriptcopy.com/'; 
compareuris[2] = 'http://www.www.scriptcopy.com/'; 
compareuris[3] = 'https://www.www.scriptcopy.com/'; 
compareuris[4] = 'http://scriptcopy.com/'; 
compareuris[5] = 'https://scriptcopy.com/'; 
compareuris[6] = 'http://www.scriptcopy.com/'; 
compareuris[7] = 'https://www.scriptcopy.com/'; 
searchuri = 'http://www.google.com/search?'; 
searchuri += 'q='+ encodeURIComponent(uri) +'&btnG=Search+Directory&hl=en&cat=gwd%2FTop'; 
req = new XMLHttpRequest(); 
req.open('GET', searchuri, true); 
req.onreadystatechange = function (aEvt) { 
    if (req.readyState == 4) { 
     if(req.status == 200) { 
      searchcontents = req.responseText; 
      parsedHTML = sc_HTMLParser(searchcontents); 
      sitefound = sc_sitefound(compareuris, parsedHTML); 
     } 
    } 
} 
req.send(null); 
function sc_HTMLParser(aHTMLString){ 
    var parseDOM = content.document.createElement('div'); 
    parseDOM.appendChild(Components.classes['@mozilla.org/feed-unescapehtml;1'] 
     .getService(Components.interfaces.nsIScriptableUnescapeHTML) 
     .parseFragment(aHTMLString, false, null, parseDOM)); 
    return parseDOM; 
} 
function sc_sitefound(compareuris, parsedHTML) { 
    gclasses = parsedHTML.getElementsByClassName('g'); 
    alert('test 1'); 
    for (i = 0; i < gclasses.length; i++) { 
     alert(i); 
     gclass = gclasses[i]; 
     atags = gclass.getElementsByTagName('a'); 
     tag1 = atags[0]; 
     hrefattribute1 = tag1.getAttribute('href'); 
     uri1 = hrefattribute1; 
     compareduris = sc_compareuris(uri1, compareuris); 
     alert('test 2'); 
     if (compareduris) { 
      sitefound = uri1; 
      return sitefound; 
      alert('test 3'); 
     } 
     alert('test 4'); 
    } 
    return null; 
} 
function sc_compareuris(uri, compareuris) { 
    for (i = 0; i < compareuris.length; i++) { 
     compareuri = compareuris[i]; 
     if (uri == compareuri) { 
      return true; 
     } 
    } 
    return false; 
} 

聚焦：

alert('test 1'); 
    for (i = 0; i < gclasses.length; i++) { 
     alert(i); 

爲什麼和如何解決？

Answer 1

我以前在IE中遇到過這樣的問題。你應該總是使用var在for循環，以確保i是局部範圍：

alert('test 1'); 
for (var i = 0; i < gclasses.length; i++) { 
    alert(i); 
    // etc... 
} 

除非你在同一範圍內事先聲明變量：

var i; 
alert('test 1'); 
for (i = 0; i < gclasses.length; i++) { 
    alert(i); 
    // etc... 
} 

參見：

Variable scope in Javascript for loop
http://developer.mozilla.org/En/Core_JavaScript_1.5_Reference/Statements/Var

Answer 2

你有沒有其他的提醒，沒有粘貼？如果將其更改爲：

alert('test 1, gclasses.length = '+gclasses.length); 
for (var i = 0; i < gclasses.length; i++) { 
    alert(i); 

我想知道該循環是否正在執行？

Answer 3

在您使用的每個函數中聲明本地變量（本例中爲i）。如果你給一個變量賦值（即使是for循環），它也會變成一個全局變量，並且可能會同時運行其他函數。