時不同的結果見http://jsfiddle.net/aEEUN/正則表達式:使用後向引用
爲什麼當我使用反向引用與未backrefences,我得到不同的結果?
var str = "Hello World\nHello ";
document.write("Without backreference: <br />");
var match = str.match(/\S(?![\s\S]*\S)/);
document.write("- match.index: " + match.index + "<br />"); // index is 16
document.write("With backreference: <br />");
var match = str.match(/(\S)(?![\s\S]*\1)/);
document.write("- match.index: " + match.index); // index is 6