javascript中的obj ['']是什么意思？

Question

Toward the bottom of this javascript file , there is a line

return map[""];

where map is an associative array of objects with parent/child relationships. After calling map[""] the returned structure is a transformation into a hierarchical array. What is really going on under the hood here and where is this syntax documented? (It's hard searching for such empty strings on the net.)

Answer 1

It just reads the empty string property of map , just like how this:

map["a"]

is the same as

map.a

However, you can't just do

map.

so that's why they do

map[""]

This is generated by the function find which ends when the strings become empty, which is why the final element will be found in map[""] .