jiyihui

我能问下一开始为啥要用闭包保存变量吗，好处在哪里

1. 4 2. ``` arr = arr.filter(option => option) ``` 3. [1, NaN, undefined, NaN] 4. ```const arr3 = arr.concat(arr2)``` 5. ```Array.from(new Set(arr3))```

1. ``` var aList = document.querySelectorAll('a')``` 2. ``` var links = document.links``` 3. ```js var linkArray = Array.from(document.links); linkArray.forEach(item => { if (item.href && item.href.indexOf('javascript:') === 0) { item.setAttribute('role', 'button')...