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1. When the function is created using the function keyword the value of this is the object left of the dot of the function which is called
2. If there is no object left of the dot then the value of this inside a function is often the global object (global in node, window in browser). I wouldn't recommend using the this keyword here because it is less explicit than using something like window!
3. There exist certain constructs like arrow functions and functions created using the Function.prototype.bind() a function that can fix the value of this. These are exceptions of the rule but are really helpful to fix the value of this.

Example in nodeJS

Let me walk you through the outputs 1 by 1 (ignoring the first log starting from the second):

1. When the function is created using the function keyword the value of this is the object left of the dot of the function which is called
2. If there is no object left of the dot then the value of this inside a function is often the global object (global in Node.js and window in a browser). I wouldn't recommend using the this keyword here because it is less explicit than using something like window!
3. There exist certain constructs like arrow functions and functions created using the Function.prototype.bind() a function that can fix the value of this. These are exceptions of the rule, but they are really helpful to fix the value of this.

Example in Node.js

Let me walk you through the outputs one by one (ignoring the first log starting from the second):

this in JS:

The value of this in JS is 100% determined by how a function is called, and not how it is defined. We can relatively easily find the value of this by the 'left of the dot rule':

1. this is obj2 because of the left of the dot rule, we can see how test1 is called obj2.test1();. obj2 is left of the dot and thus the this value.
2. Even though obj2 is left of the dot, test2 is bound to obj1 via the bind() method. So the this value is obj1.
3. obj2 is left of the dot from the function which is called: obj2.test3(). Therefore obj2 will be the value of this.
4. In this case: obj2.test4() obj2 is left of the dot. However, arrow functions don't have their own this binding. Therefore it will bind to the this value of the outer scope which is the module.exports an object which was logged in the beginning.
5. We can also specify the value of this by using the call function. Here we can pass in the desired this value as an argument, which is obj2 in this case.

this in JavaScript:

The value of this in JavaScript is 100% determined by how a function is called, and not how it is defined. We can relatively easily find the value of this by the 'left of the dot rule':

1. this is obj2 because of the left of the dot rule, we can see how test1 is called obj2.test1();. obj2 is left of the dot and thus the this value.
2. Even though obj2 is left of the dot, test2 is bound to obj1 via the bind() method. The this value is obj1.
3. obj2 is left of the dot from the function which is called: obj2.test3(). Therefore obj2 will be the value of this.
4. In this case: obj2.test4() obj2 is left of the dot. However, arrow functions don't have their own this binding. Therefore it will bind to the this value of the outer scope which is the module.exports an object which was logged in the beginning.
5. We can also specify the value of this by using the call function. Here we can pass in the desired this value as an argument, which is obj2 in this case.

The value of this in JS is 100% determined by how a function is called, and not how it is defined. We can relatively easy find the value of this by the 'left of the dot rule':

1. When function are created using the function keyword the value of this is the object left of the dot of the function which is called
2. If there is no object left of the dot then the value of this inside a function is often the global object (global in node, window in browser). I wouldn't recommend using the this keyword here because it is less explicit than using something like window!
3. There exists certain constructs like arrow functions and functions created using the Function.prototype.bind() function which can fix the value of this. These are exceptions of the rule but are really helpful to fix the value of this.

1. this is obj2 because of the left of the dot rule, we can see how test1 is called obj2.test1();. obj2 is left of the dot and thus the this value.
2. Even though obj2 is left of the dot, test2 is bound to obj1 via the bind() method. So the this value is obj1.
3. obj2 is left of the dot from the function which is called: obj2.test3(). Therefore obj2 will be the value of this.
4. In this case: obj2.test4() obj2 is left of the dot. However arrow function don't have their own this binding. Therefore it will bind to the this value of the outer scope which is the module.exports object which was logged in the beginning.
5. We can also specify the value of this by using the call function. Here we can pass in the desired this value as an argument, which is obj2 in this case.

The value of this in JS is 100% determined by how a function is called, and not how it is defined. We can relatively easily find the value of this by the 'left of the dot rule':

1. When the function is created using the function keyword the value of this is the object left of the dot of the function which is called
2. If there is no object left of the dot then the value of this inside a function is often the global object (global in node, window in browser). I wouldn't recommend using the this keyword here because it is less explicit than using something like window!
3. There exist certain constructs like arrow functions and functions created using the Function.prototype.bind() a function that can fix the value of this. These are exceptions of the rule but are really helpful to fix the value of this.

1. this is obj2 because of the left of the dot rule, we can see how test1 is called obj2.test1();. obj2 is left of the dot and thus the this value.
2. Even though obj2 is left of the dot, test2 is bound to obj1 via the bind() method. So the this value is obj1.
3. obj2 is left of the dot from the function which is called: obj2.test3(). Therefore obj2 will be the value of this.
4. In this case: obj2.test4() obj2 is left of the dot. However, arrow functions don't have their own this binding. Therefore it will bind to the this value of the outer scope which is the module.exports an object which was logged in the beginning.
5. We can also specify the value of this by using the call function. Here we can pass in the desired this value as an argument, which is obj2 in this case.