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wxml中不能用typeof判断undefined?Can't use typeof to judge undefined in wxml?
wxml中不能用typeof判断undefined?
js中
data:{ // nothing }
wxml中
<view wx:if="{{typeof(foo)!=='undefined'}}">hello view>
这里的hello不会展示,经测试wxml中的typeof(foo)输出是 undefined,但是表达式并不成立。
wxml中
foo!==undefined typeof(foo)!=='undefined' typeof(foo)!==undefined
js中是成立的,为什么wxml中不保持一致?
typeof(foo)!=='undefined'
Data: {/ / nothing} wxml < view Wx: if = {{typeof (foo)! = = = = ='undefined '}} > > Hello > in wxml, the output of typeof (foo) in wxml is undefined, but the expression does not hold. In wxml, foo! = = undefined / / truetypeof (foo)! = = = = = = = undefined '/ / false type (foo)! = = undefined / / false JS is true. Why is it inconsistent in wxml? typeof(foo)!=='undefined' // true
wx:if="{{foo}}"就标识了 不为空不为null不为undefined不为负