code: function getExpression(expr){
  //console.debug(MODULE, expr)
  	let val = (expr + '').trim();
  	if ( options.ExpressionUnescapeStart.length > options.ExpressionStart.length ) {
  		// 长的先匹配
  		if ( val.startsWith(options.ExpressionUnescapeStart) && val.endsWith(options.ExpressionUnescapeEnd) ) {
  			return '(' + val.substring(options.ExpressionUnescapeStart.length, val.length - options.ExpressionUnescapeEnd.length) + ')';
  		}else if ( val.startsWith(options.ExpressionStart) && val.endsWith(options.ExpressionEnd) ) {
  			return options.NameFnEscapeHtml + '(' + val.substring(options.ExpressionStart.length, val.length - options.ExpressionEnd.length) + ')';
  		}
  	}else{
  		if ( val.startsWith(options.ExpressionStart) && val.endsWith(options.ExpressionEnd) ) {
  			return options.NameFnEscapeHtml + '(' + val.substring(options.ExpressionStart.length, val.length - options.ExpressionEnd.length) + ')';
  		}else if ( val.startsWith(options.ExpressionUnescapeStart) && val.endsWith(options.ExpressionUnescapeEnd) ) {
  			return '(' + val.substring(options.ExpressionUnescapeStart.length, val.length - options.ExpressionUnescapeEnd.length) + ')';
  		}
  	}
  	return '"' + lineString(val) + '"';
  }
docs: 取表达式代码（删除两边表达式符号）