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We already discussed an about use effect and we also know that there is a clean up when the component

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is monitored but sometimes not everything like this another.

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Yeah you say from a certain cold we move the listener.

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And in this case yes.

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Where can apps do to use the Web can however deal with these problems and to make a example more clear.

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We are going to add a header to this fingers to example

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in order to create a b among component.

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We have to create a component.

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So we go to create a new folder called components and inside the components we create a component dotty

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as

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an inside the component.

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We will use.

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You will stay

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and we create a constant command and effect kind

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equal to a use day and then we create a fake fetch from the Jones that pretend is fetching a new rally

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or fund a we both server

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and every two seconds it will increase the Congress to buy one

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and we display the value inside the header and then we also create a button to trigger the effect fetch

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functions.

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Then we back to the app J S and import the component from components.

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And then we are going to demonstrate that a mounting component problems.

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So we create a header named as a main component and we are going to import the component here.

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Now we also have to create a button to trigger the toggle showing i.e. functions.

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So now when you click on the toggle component it will hide the component and when you click the effect

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fetch it will still can at the White House by one.

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But when you toggle but when you click the effect fetch button and then you toggle the component it

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will destroy it an error because the components already are monitored but we are going to perform the

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update.

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So what can we do is to go to the component and in order to check the component is a mindset.

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We have to use to use if that and then we create a component where

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and then add a cleanup part we change the component where to boss.

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We also need to import the use of where.

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So now we have these components top for orange.

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So now we have the components RAF block curve and we can use these to check whether it is a monitor.

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So we will only go 2 seconds only when the component with Dr. orange is equal to true.

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Otherwise we will not update it can rarely use.

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So now we can try again.

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Now if we were not so the areas even where we clicked on effect fetch to make it more clear we can create

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a console not to let us know that the function is really executed.

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So now we kick on the fact fashion and talk with the components.

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You will not show the arrows but if the component is still here it will update you radically.