如何理解Array.apply(null, {length:5})的{length:5}?
我测试过Array.apply(null, {length:5}) //返回[undefined, undefined, undefined, undefined, undefined]
Array.apply(null, [{length:5}])和Array({length:5})返回的结果是一样的,为
[[object Object] {
length: 5
}]
第二、三还能理解！第一种怎么理解？
三叔2016-10-28 09:34:17
Array.apply(null, {length: 5}) length为特殊字段，意思是生成一个长度为5的数组，由于没赋值，所以都是undefined, 如果要赋值，可以这样
console.log(Array.apply(null, {0:'a', 1: 'b', 2: 'c', 3: 'd', 4: 'e', length:5})); //["a", "b", "c", "d", "e"]和ES6的Array.from有点类似, Array.from