在两个$$符号之间书写时识别 [英] Recognize when writing in between two $$ signs

问题描述

我有一个文本字段，正在其中编写一些文本.

I have a textfield in which I'm writing some text.

为简单起见，我希望alert('Boom!')每次在两个$$之间开始写入时都跳出来.

For the sake of simplicity, I want that alert('Boom!') jumps out every time I start writing in between two $$.

例如，我有一个空白的文本字段并开始键入(光标为"|"符号)

For example I have a blank textfield and start typing (cursor is "|" sign)

Today is a really nice day|

什么也没有发生，请开始输入

nothing happens, start typing

Today is a really nice day, $|$

什么都没有，但是现在当我开始输入

still nothing, but now when I start typing

Today is a really nice day, $someText|$

在这些美元符号之间的每个字母，警告框都应跳出.

alert box should jump out for each letter in between those dollar signs.

我为什么需要这种功能?每当用户开始键入自己的方程式时，我都希望进行实时方程式预览(MathJax渲染)，我可以通过$$符号来识别它是一个方程式(介于两者之间的所有内容都将被渲染).

Why do I need that kind of feature? I want live-equation-preview (MathJax rendering) every time user starts typing his/her equation, and I can recognize it's an equation by $$ signs (everything in between is rendered).

编辑:文本字段中可能有多个$$.脚本必须识别当前处于活动状态的光标(光标位置在其$$之间).

Multiple $$'s are possible in textfield. Script must recognize the one which is currently active (cursor position is between it's $$'s).

推荐答案

您可以使用jQuery插入符

You can use jQuery caret plugin

http://examplet.buss.hk/download/download. php?plugin = caret.1.01

注意:编辑并删除第8行中的这些字符Ôªø

和replace功能. (不替换任何东西，而是使用匹配模式的索引)

and replace funcition. ( not to replace anything but to use the index of matched pattern )

$("#myText").bind("keyup", function(e){
     var text = $(this).val();
     var caret = $(this).caret().start;

     if(text && text.length > 0){
        text.replace(/\$.*?\$/g, function(m, n){
           if(caret > n && caret < (n + m.length)){
              alert("BOOM");
           }
        });
     }
});

演示: http://jsfiddle.net/xqXXb/

仅显示如何执行此操作.您可以改善这一点.

Just showing how to do it. You can improve this.

使用

$("#myText").bind("keyup keydown change", function(e){ ...

以获得更好的结果.

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