Answer 1

为什么把var name改成let name，结果就变成Hello Tom了呢，求大佬解答

let声明变量会建立块级作用域，不会产生变量提升

Answer 2

var str = '[abc[bcd[def]]]';
console.log(fn(str));
function fn(strs) {
	var arr = strs.replace('[', '').replace(/]/g, '').split('[');
	// console.log('arr: ', arr);
	var res = {};
	var pointer = res;
	for (var i = 0; i < arr.length; i ++) {
		pointer.value = arr[i];
		if (i < arr.length - 1) {
			pointer.children = {};
			pointer = pointer.children;
		}
	}
	return res;
}