javascript - Mind twisting implied this.var access - 


x = {}  function f1 () {     this.v1 = 'cool'     try { console.log('v1:', v1) } catch(e){ console.log('error') } }  f1.bind(x)() f1() f1.bind(x)() f1()

output:

error v1: cool v1: cool v1: cool

please explain why code prints error once, , cool.

why v1 without this work @ in first place?

first, you're logging not this.v1, v1. reference global v1 variable supposed defined on window. every time log not x.v1, window.v1.

this in function without bounded scope refers global window. when call first time, v1 created on x, when call second time, created on window.


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