Method containing “this” keyword works different when it's called in another method vs when it's assigned...
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This question already has an answer here:
How does the “this” keyword work?
23 answers
Having the following code, the output is undefined when calling the Play method from my object instance while I was expecting the 'this' keyword to reference the global variable and display "Football" in lack of a PlayGound's scope variable.
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();Now, invoking the Play() at constructor level, without passing it's reference to a local variable the output is "Football".
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();Can someone explain the reason why those two aproaches behave differently?
javascript constructor this ecmascript-5
edited Nov 24 '18 at 17:20
Patrick Roberts
21.3k33777
asked Nov 24 '18 at 17:19
george sacageorge saca
205
marked as duplicate by Bergi javascript
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Nov 24 '18 at 17:53
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
add a comment |
This question already has an answer here:
How does the “this” keyword work?
23 answers
Having the following code, the output is undefined when calling the Play method from my object instance while I was expecting the 'this' keyword to reference the global variable and display "Football" in lack of a PlayGound's scope variable.
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();Now, invoking the Play() at constructor level, without passing it's reference to a local variable the output is "Football".
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();Can someone explain the reason why those two aproaches behave differently?
javascript constructor this ecmascript-5
edited Nov 24 '18 at 17:20
Patrick Roberts
21.3k33777
asked Nov 24 '18 at 17:19
george sacageorge saca
205
marked as duplicate by Bergi javascript
Users with the javascript badge can single-handedly close javascript questions as duplicates and reopen them as needed.
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Nov 24 '18 at 17:53
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
1
It doesn't matter where it is called, it matters how it is called -obj.Play()vs.Play(). You also should use strict mode.
– Bergi
Nov 24 '18 at 17:53
add a comment |
This question already has an answer here:
How does the “this” keyword work?
23 answers
Having the following code, the output is undefined when calling the Play method from my object instance while I was expecting the 'this' keyword to reference the global variable and display "Football" in lack of a PlayGound's scope variable.
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();Now, invoking the Play() at constructor level, without passing it's reference to a local variable the output is "Football".
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();Can someone explain the reason why those two aproaches behave differently?
javascript constructor this ecmascript-5
edited Nov 24 '18 at 17:20
Patrick Roberts
21.3k33777
asked Nov 24 '18 at 17:19
george sacageorge saca
205
This question already has an answer here:
How does the “this” keyword work?
23 answers
Having the following code, the output is undefined when calling the Play method from my object instance while I was expecting the 'this' keyword to reference the global variable and display "Football" in lack of a PlayGound's scope variable.
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();Now, invoking the Play() at constructor level, without passing it's reference to a local variable the output is "Football".
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();Can someone explain the reason why those two aproaches behave differently?
This question already has an answer here:
How does the “this” keyword work?
23 answers
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();javascript constructor this ecmascript-5
javascript constructor this ecmascript-5
edited Nov 24 '18 at 17:20
Patrick Roberts
21.3k33777
asked Nov 24 '18 at 17:19
george sacageorge saca
205
edited Nov 24 '18 at 17:20
Patrick Roberts
21.3k33777
asked Nov 24 '18 at 17:19
george sacageorge saca
205
edited Nov 24 '18 at 17:20
Patrick Roberts
21.3k33777
edited Nov 24 '18 at 17:20
Patrick Roberts
21.3k33777
edited Nov 24 '18 at 17:20
Patrick Roberts
21.3k33777
21.3k33777
asked Nov 24 '18 at 17:19
george sacageorge saca
205
asked Nov 24 '18 at 17:19
george sacageorge saca
205
asked Nov 24 '18 at 17:19
george sacageorge saca
205
205
marked as duplicate by Bergi javascript
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Nov 24 '18 at 17:53
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
marked as duplicate by Bergi javascript
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Nov 24 '18 at 17:53
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
1
It doesn't matter where it is called, it matters how it is called -obj.Play()vs.Play(). You also should use strict mode.
– Bergi
Nov 24 '18 at 17:53
add a comment |
1
It doesn't matter where it is called, it matters how it is called -obj.Play()vs.Play(). You also should use strict mode.
– Bergi
Nov 24 '18 at 17:53
1
1
It doesn't matter where it is called, it matters how it is called -
obj.Play() vs. Play(). You also should use strict mode.– Bergi
Nov 24 '18 at 17:53
It doesn't matter where it is called, it matters how it is called -
obj.Play() vs. Play(). You also should use strict mode.– Bergi
Nov 24 '18 at 17:53
add a comment |
1 Answer
1
active
oldest
votes
The first one outputs undefined very simply because obj does not have a game property. That can be fixed like this:
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.game = game;
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();The second snippet is bad practice because it relies on mechanics of non-strict mode simple calls in order to work.
If you change the second snippet to strict mode it will error because this in simple calls is undefined instead of window:
"use strict";
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();If you use let or const declaration for game, the second snippet will output undefined because those top-level declarations do not attach to the global scope window:
let game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();answered Nov 24 '18 at 17:31
Patrick RobertsPatrick Roberts
21.3k33777
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
The first one outputs undefined very simply because obj does not have a game property. That can be fixed like this:
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.game = game;
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();The second snippet is bad practice because it relies on mechanics of non-strict mode simple calls in order to work.
If you change the second snippet to strict mode it will error because this in simple calls is undefined instead of window:
"use strict";
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();If you use let or const declaration for game, the second snippet will output undefined because those top-level declarations do not attach to the global scope window:
let game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();answered Nov 24 '18 at 17:31
Patrick RobertsPatrick Roberts
21.3k33777
add a comment |
The first one outputs undefined very simply because obj does not have a game property. That can be fixed like this:
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.game = game;
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();The second snippet is bad practice because it relies on mechanics of non-strict mode simple calls in order to work.
If you change the second snippet to strict mode it will error because this in simple calls is undefined instead of window:
"use strict";
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();If you use let or const declaration for game, the second snippet will output undefined because those top-level declarations do not attach to the global scope window:
let game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();answered Nov 24 '18 at 17:31
Patrick RobertsPatrick Roberts
21.3k33777
add a comment |
The first one outputs undefined very simply because obj does not have a game property. That can be fixed like this:
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.game = game;
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();The second snippet is bad practice because it relies on mechanics of non-strict mode simple calls in order to work.
If you change the second snippet to strict mode it will error because this in simple calls is undefined instead of window:
"use strict";
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();If you use let or const declaration for game, the second snippet will output undefined because those top-level declarations do not attach to the global scope window:
let game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();answered Nov 24 '18 at 17:31
Patrick RobertsPatrick Roberts
21.3k33777
The first one outputs undefined very simply because obj does not have a game property. That can be fixed like this:
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.game = game;
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();The second snippet is bad practice because it relies on mechanics of non-strict mode simple calls in order to work.
If you change the second snippet to strict mode it will error because this in simple calls is undefined instead of window:
"use strict";
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();If you use let or const declaration for game, the second snippet will output undefined because those top-level declarations do not attach to the global scope window:
let game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.game = game;
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
this.game = game;
this.Play = Play;
}
var obj = new PlayGround();
obj.Play();"use strict";
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();"use strict";
var game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();let game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();let game = "Football";
function Play() {
console.log(this.game)
}
function PlayGround() {
Play();
}
var obj = new PlayGround();answered Nov 24 '18 at 17:31
Patrick RobertsPatrick Roberts
21.3k33777
answered Nov 24 '18 at 17:31
Patrick RobertsPatrick Roberts
21.3k33777
answered Nov 24 '18 at 17:31
Patrick RobertsPatrick Roberts
21.3k33777
answered Nov 24 '18 at 17:31
Patrick RobertsPatrick Roberts
21.3k33777
21.3k33777
add a comment |
add a comment |
1
It doesn't matter where it is called, it matters how it is called -
obj.Play()vs.Play(). You also should use strict mode.– Bergi
Nov 24 '18 at 17:53