.filter（）在javascript / typescript中(.filter() in javascript/typescript)

.filter（）在javascript / typescript中(.filter() in javascript/typescript) .filter( (item) => { console.log(this.timeFilter); // line 1 if(this.timeFilter == NaN ) { return true; } // line 2 console.log("why log this?"); // line 3 return item.endTime < this.timeFilter; } )

我的代码是上面的，我有一个问题，即使this.timeFilter == NaN，它不会去第2行，但实际上去第3行，不太确定发生了什么

NaN // line 1 output why log this? // line 3 output happen .filter( (item) => { console.log(this.timeFilter); // line 1 if(this.timeFilter == NaN ) { return true; } // line 2 console.log("why log this?"); // line 3 return item.endTime < this.timeFilter; } )

my code is above, I have a question that even if the this.timeFilter == NaN, it does not go the line 2, but go line 3 actually, not so sure what happened

NaN // line 1 output why log this? // line 3 output happen

最满意答案

NaN == NaN在javascript中返回false 。 这是为了防止像这样的操作

'somename' / 5 == 'someothername' / 5; // should not return true (both are NaN)

使用isNaN ：

if(this.timeFilter == NaN)实际应该是if(!isNaN(this.timeFilter))

NaN == NaN returns false in javascript. This is to prevent operations like

'somename' / 5 == 'someothername' / 5; // should not return true (both are NaN)

Use isNaN:

if(this.timeFilter == NaN) should be actually if(!isNaN(this.timeFilter))