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December 20, 2015 02:49
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How is a 'this' argument changed in javascript ? ref: [じゃあ this の抜き打ちテストやるぞー](http://qiita.com/KDKTN/items/0b468a07410d757ac609)
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <title></title> | |
| <script type="text/javascript"> | |
| 'use strict'; | |
| var a, b, c, e, f, fnc; | |
| a = function(){ | |
| console.log(this && this.constructor); | |
| console.log(this); | |
| var self = this; | |
| var infnc = function(){ | |
| console.log(self && self.constructor); | |
| console.log(self); | |
| console.log(this && this.constructor); | |
| console.log(this); | |
| } | |
| infnc(); | |
| }; | |
| b = { | |
| a: a | |
| }; | |
| c = { | |
| b: b | |
| }; | |
| console.log('basic ---------------------------------'); | |
| // window | |
| // strict: undefined | |
| a(); | |
| // b | |
| // infnc: undefined | |
| b.a(); | |
| // b | |
| // infnc: undefined | |
| c.b.a(); | |
| console.log('change context ---------------------------------'); | |
| // window | |
| // strict: undefined | |
| fnc = a; | |
| fnc(); | |
| // window | |
| // strict: undefined | |
| fnc = b.a; | |
| fnc(); | |
| // window | |
| // strict: undefined | |
| fnc = c.b.a; | |
| fnc(); | |
| // b | |
| // infnc: undefined | |
| fnc = c.b; | |
| fnc.a(); | |
| console.log('methods ---------------------------------'); | |
| function d(){ | |
| console.log(this && this.constructor); | |
| console.log(this); | |
| var self = this; | |
| var infnc = function(){ | |
| console.log(self && self.constructor); | |
| console.log(self); | |
| console.log(this && this.constructor); | |
| console.log(this); | |
| } | |
| infnc(); | |
| this.myfnc = function(){ | |
| console.log(self && self.constructor); | |
| console.log(self); | |
| console.log(this && this.constructor); | |
| console.log(this); | |
| } | |
| } | |
| e = { | |
| a: a | |
| } | |
| // d | |
| // infnc: undefined | |
| f = new d(); | |
| // d | |
| f.myfnc(); | |
| // e.a | |
| // infnc: undefined | |
| new e.a(); | |
| console.log('apply(call) ---------------------------------'); | |
| // window | |
| a.apply(window); | |
| // 42 | |
| a.apply(42); | |
| // window | |
| // strict: undefined | |
| a.apply(); | |
| // window | |
| // strict: undefined | |
| a.apply(undefined); | |
| console.log('etc ---------------------------------'); | |
| // window | |
| // strict: undefined | |
| (function(){ | |
| console.log(this); | |
| console.log(('a',eval)('this')); | |
| })(); | |
| // window | |
| // strict: window | |
| new Function('console.log(this && this.constructor);console.log(this);')() | |
| </script> | |
| </head> | |
| <body> | |
| </body> | |
| </html> |
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じゃあ this の抜き打ちテストやるぞー