访问2D JavaScript数组

问题描述：

我试图编写一段简单的JavaScript读取CSV（粘贴到网页上的textarea）并生成SQL插入语句，但是当我引用2D数组时，我一直收到未定义的值。。访问2D JavaScript数组

请帮忙！

var ret = ""; 
//alert("called"); 
//split the textarea into rows of text 
var lines = text.split("\n");   
//the first line of text is the table name 
var table = lines[0];     

//the second line of text is an array of the attribute names 
var attrnames = lines[1].split(",");   
var values = new Array(); 

//create a new array for each attribute 
for (var i = 0; i < attrnames.length; i++) { 
    //the length of each array is the total number of rows 
    //of text - 2 (title row and attr row) 
    values.push(new Array(lines.length - 2));  
} 

//for each subsequent row, push the values to the appropriate arrays 
for (var i = 2; i < lines.length; i++) { 
    //get the current row (value, value, value, value) 
    var thisrow = lines[i].split(",");   
    for (var j = 0; j < attrnames.length; j++) { 
     //add the j-th attribute (thisrow[j]) to its array (values[j]) 
     values[j].push(thisrow[j]);    
    } 
} 

var insertIntoTable = ""; 
var tableName = ""; 
var attrList = ""; 
var valueList = ""; 
var lead = ""; 

//loop through each row 
for (var k = 2; k < lines.length; k++) { 

    // --- ONE STATEMENT --- 
    //create the statements 
    insertIntoTable = "insert into table `"; 
    tableName = table; 
    attrList = "` ("; 
    valueList = "("; 
    for (var i = 0; i < attrnames.length; i++){ 
     attrList += "`" + attrnames[i] + "`,"; 
    } 

    //trim the last comma, then add the closing parenthesis. 
    attrList = attrList.substring(0, attrList.length-1) + ") "; 
    lead = insertIntoTable + tableName + attrList;  

    for (var i = 0; i < attrnames.length; i++) { 
     //this always points to undefined 
     valueList += "'" + values[i][k-2] + "', "; 
    } 

    lead += (" values " + valueList); 
    lead = lead.substring(0, lead.length-2) + ");\n"; 

    ret += lead; 

} 

alert(ret);

请勿将csv粘贴到文本框中，让它们通过文件附件将其上传 – 2013-02-26 00:31:19

这不是某人粘贴到小Bobby表的链接吗？ – YXD 2013-02-26 00:32:32

http://xkcd.com/327/ – 2013-02-26 00:33:25

答

在JavaScript中，您不需要设置数组的长度。它们更像ArrayLists或其他东西;阅读更多在MDN's documentation。

当你

var x = new Array(10); // array with "length" set to 10 
x.push("somevalue");

则该值将在x[10]插入 - 在列表的末尾。将其记录在控制台中以便自己查看。

因此，要么删除push()并改为使用绝对指示符，要么将该数组初始化为空 - 最好使用array literal syntax：[]。那么你的代码的相关区域应该是这样的：

//create a new empty array for each attribute 
for(var i = 0; i<attrnames.length; i++){ 
    values.push([]); 
}

谢谢Bergi，你是个绅士和学者:) – connerc 2013-02-26 00:43:58

答

你正在长n，其中n是行数，并然后你在数据n更多元素推的数组。从0开始长数组，你将被罚款：

//create a new array for each attribute 
for(var i = 0; i<attrnames.length; i++){ 
    values.push(new Array(0)); // or '[]' -> the length of each array **will be** the total number of rows of text-2 (title row and attr row) 
}

我想补充警告说，粘贴的数据会容易出现大量的错误和潜在的安全问题，如SQL注入攻击。除此之外，如果数据末尾还有额外的\n秒，会发生什么情况？你将会得到更多未定义的数据。

访问2D JavaScript数组

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