SOURCE

 function GetAnswerEx(text, start, answerCount, iTag) {
	 if (text == null || text == '') {
		 return -1;
	 }
	 var v_str = text;
	 var v_temp_str = '';
	 var iLen = -1;
	 var v_find = -1;
	 var v_start_Index = -1;
	 var v_temp_index = -1;
	 var v_temp_index1 = -1;
	 //查询v_str中的star
	 v_start_Index = v_str.indexOf(start);
	 while (v_start_Index != -1) {
		 //"Answer":"
         
		 v_start_Index = v_str.indexOf(start, v_temp_index);
		 v_temp_index = v_str.indexOf('",', v_start_Index + start.length);

		 v_temp_index1 = v_str.indexOf('"}', v_start_Index + start.length);
		 if (v_temp_index1 < v_temp_index && v_temp_index1 > -1) {
			 v_temp_index = v_temp_index1;
		 }

		 if (v_start_Index == -1) {
			 break;
		 }
		 if (v_temp_index == -1) {
			 break;
		 }
          
		 //截取字符串
		 if (v_temp_index > 0) {
			 v_temp_str = v_str.substr(v_start_Index + start.length, v_temp_index - (v_start_Index + start.length));
		 }
		 //判断v_temp_str的长度
		 iLen = v_temp_str.length;
		 if (iLen >= answerCount && iTag == 1) {
			 v_find = 1;
			 break;
		 } else if (iLen > answerCount && iTag == 0) {
			 v_find = -1;
			 break;
		 }
		 if (iTag == 0 && v_find == -1) {
			 v_find = 1;
		 }
	 }
	 return v_find;
 }
 let b='{"AllTestID":"4004613","Answer":"a","Type":"XTEST","BookTestNo":"128","Title":"测量体温如何判断自己发热,平静状态下超过(   )°C","HasImg":0,"Difficulty":"","Explain":"","TestPoint":"","Word":"","Summary":"","ReferenceTranslation":"","HighFrequency":"","DifficultSentences":"","SelectedItems":[{"ItemName":"A","Content":"36.8"},{"ItemName":"B","Content":"37"},{"ItemName":"C","Content":"37.3"},{"ItemName":"D","Content":"37.7"}]}'
 let a= GetAnswerEx(b, '"Answer":"', 2, 0) == -1 ? 0 : 1;
 console.log(a)