text: 'use strict';
  // 检查background子属性中是否含有IE不认识的值
  const bgSubKeyWord = {
  	color: /\b(?:rgba|hsla?)\(/i,
  	repeat: /\b(?:round|space?)\b/i,
  	attachment: /\blocal\b/i,
  };
  
  // 检查background属性中是否有IE不认识的关键字
  const bgKeyWord = [
  	// border-box | padding-box | content-box
  	/\b(?:border|padding|content)-box\b/,
  	// auto | cover | contain | text
  	/\b(auto|cover|contain|text)\b/,
  	// 长度值
  	/\/\s*(?:\d*\.)?\d+(?:[a-z]+?|%)\b/,
  ].concat(Object.keys(bgSubKeyWord).map(function (prop) {
  	return bgSubKeyWord[prop];
  }));
  
  function getClearValue (value) {
  	return value.replace(/\b(?:url|(?:rgb|hsl)a?)\([^()]+\)/i, '');
  }
  
  function hasMultipleBg (value) {
  	return /,/.test(value);
  }
  
  function hasBgKeyWord (decl) {
  	const prop = /^background(?:-(\w+))?$/i.exec(decl.prop);
  	if (!prop) {
  		return;
  	}
  
  	if (prop[1]) {
  		const regexp = bgSubKeyWord[prop[1].toLowerCase()];
  		return (regexp && regexp.test(decl.value)) || hasMultipleBg(getClearValue(decl.value));
  	} else {
  		const value = getClearValue(decl.value);
  		return bgKeyWord.some(function (regexp) {
  			return regexp.test(value);
  		}) || hasMultipleBg(value);
  	}
  }
  
  module.exports = hasBgKeyWord;
  