Question

我有一个带textarea标签的html文件，其中我将复制并粘贴一些带有多行的文本，我希望使用javascript分别在三个不同的变量中分别获取最后三行。 textarea被分配了一个id =＆＃34; txt＆＃34;。 点击的功能被分配到html文件中的按钮。

function clicked(){
var txt = document.getElementById("txt");
var original = txt.value; //original text transfered to original variable

var lastline =  //add last line in this variable

var secondlast = //add second last line in this variable

var thirdlast = //add third last line in this variable

var modified = //add text without these three lines in this variable


console.log(lastline); //how are you
console.log(secondlast); //now is the time
console.log(thirdlast); //helloo  there
console.log(modified); //school data is the important
//checking home
//not there
}

在textarea中输入的文字：

school data is the important
checking home
not there
helloo  there
now is the time
how are you

输出：

how are you

now is the time

helloo  there

school data is the important
checking home
not there

Answer 1

简单的功能：

function letsgo() {
  var area= document.getElementById("mytext"),
  //get all the lines in the textarea, seperated by \n or \r\n
      lines = area.value.match(/[^\r\n]+/g),
  //get bottom 3 lines, reverse them
      bottom3 = lines.slice(-3).reverse();

  var lastline=bottom3[0];
  var secondlast=bottom3[1];
  var thirdlast=bottom3[2];

  //get all text except bottom 3 lines, joining them together with linefeed again
  var rest = lines.slice(0, -3).join("\n");

  //glue bottom3 and rest together
  var result=bottom3.join("\n")+"\n"+rest;

  //put in the textarea again
  area.value=result;
}

Answer 2

textarea的value内的换行符用换行符而不是HTML <br>元素表示。]

您可以通过将换行符规范化为\n然后在textarea的值上调用split()方法来获取各行。

这是一个实用程序函数，它为textarea值的每一行调用一个函数：

function actOnEachLine(textarea, func) {
    var lines = textarea.value.replace(/\r\n/g, "\n").split("\n");
    var newLines, i;

    // Use the map() method of Array where available 
    if (typeof lines.map != "undefined") {
        newLines = lines.map(func);
    } else {
        newLines = [];
        i = lines.length;
        while (i--) {
            newLines[i] = func(lines[i]);
        }
    }
    textarea.value = newLines.join("\r\n");
}

var textarea = document.getElementById("txt");
var lines;  // Store your lines in an array
actOnEachLine(textarea, function(line) {
    lines.push(line) //
});

Answer 3

这很简单。

＆＃13;

var lastline,secondlast,thirdlast,modified;
function parse()
{
    var elem = document.getElementById("txt");
    var text = elem.value;
    var arr = text.replace(/\n/g,"$").split("$");
    if(arr.length) lastline = arr.pop();
    if(arr.length) secondlast = arr.pop();
    if(arr.length) thirdlast = arr.pop();
    modified = arr.join("\n");
    console.log(lastline,secondlast,thirdlast);
    console.log(modified);
}

＆＃13;

<textarea id="txt"></textarea>
<button onclick="parse()">Parse</button>

＆＃13;

如何将最后三行textarea添加到三个不同的变量？

3 个答案: