JavaScript essence (i)

Since I think JavaScript is not proficient in some knowledge points or not mastered thoroughly, so write this article is to be able to often look at these points of knowledge, and hope that in the days to come back to the study of their own way.

JavaScript functions are top-level objects that are based on lexical scopes .

What is lexical scope? function execution depends on the scope of the variable, which is determined when the function is defined, not when the function is called.

Reference

The essence of JavaScript language

JavaScript Definitive Guide (sixth edition)

JavaScript essence (i)