js 判断不为null undefind 空字符串等

// 判断是否为空 返回true/falsefunction isBlank(data) {if (data == null ||data === 'null' ||data === '' ||data === undefined ||data === 'undefined' ||data === 'unknown') {return true} else {return false}}var a = undefinedif(!isBlank(a)) {// 不为空时的代码}