取子字符串的索引位置（不在引号内的）

gistfile1.js

/**
 * 取子字符串的索引位置（不在引号内的）
 *
 * @param {String} text
 * @param {String} subject
 * @param {Integer} start
 */
var textIndexOf = function (text, subject, start) {
  if (start < 0) {
    start = text.length + start;
  } else if (isNaN(start)) {
    start = 0;
  }
  var subjectLength = subject.length;
  var quote = false;
  for (var i = start, len = text.length; i < len; i++) {
    var c = text[i];
    if (quote) {
      if (c === quote && text[i - 1] !== '\\') {
        quote = false;
      }
    } else {
      if ((c === '\'' || c === '"') && text[i - 1] !== '\\') {
        quote = c;
      } else {
        if (text.substr(i, subjectLength) === subject) {
          return i;
        } 
      }
    }
  }
  return -1;
};

console.log(textIndexOf('123456abc789100abc', 'abc'));
console.log(textIndexOf('123456abc789100abc', 'abc', 8));
console.log(textIndexOf('123456abc789100abc', 'abc', -4));
console.log(textIndexOf('123456"abc"789100abc', 'abc'));
console.log(textIndexOf('123456"abc\\"789100abc', 'abc'));
console.log(textIndexOf('123456"abc\\\'789100abc', 'abc'));