js中的false null 0 undefined '' ''(空字符串) NaN都會返回false
[]會返回true
if(!''){console.log('yes')}//yes if(!false){console.log('yes')}//yes if(!undefined){console.log('yes')}//yes if(!0){console.log('yes')}//yes if(!NaN){console.log('yes')}//yes if(!null){console.log('yes')}//yes if(![]){console.log('yes')}//不執行代碼塊,![]為false
^_^
