类数组(伪数组）：具有length和若干索引的可迭代对象 + Array.form(nodeList) + Array.prototype.slice.call(nodeList) 或者Array.prototype.map.call等 ```js co[3.手写forEach, map, filter, every, some, reduce](3.%E6%89%8B%E5%86%99forEach,map,filter,every,some,reduce.md)nst lis = document.getElementsByTagName('li') const arrlis = Array.from(lis) const arrlis = Array.prototype.slice.call(lis) console.log(arrlis); ```