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JavaScript when to use callback, many novices are not very clear about this, in order to help you solve this problem, the following small series will explain in detail for everyone, there are people who need this can learn, I hope you can gain something.

When does JavaScript use callbacks?

Callbacks are functions that are passed as arguments to another function.

With callbacks, you can call a calculator function (myCalculator) with a callback and have the calculator function run the callback after the calculation is complete:

examples

function myDisplayer（some） { document.getElementById（"demo"）。innerHTML = some;}function myCalculator（num1, num2, myCallback） { let sum = num1 + num2; myCallback（sum）;}myCalculator（5, 5, myDisplayer）;

In the example above, myDisplayer is the name of the function.

It is passed as an argument to myCalculator ().

When you pass functions as arguments, remember not to use parentheses.

Correct: myCalculator (5, 5, myDisplayer);

Error: myCalculator (5, 5, myDisplayer ());

The example above is not very exciting.

They have been simplified to explain the callback syntax to you.

Where callbacks really shine are asynchronous functions, where one function has to wait for another (for example, waiting for a file to load).

JavaScript can embed dynamic text in HTML pages. Responding to browser events. Read and write HTML elements. Verify data before it is submitted to the server. 5. Detect the browser information of visitors. Control cookies, including creation and modification. 7. Server-side programming based on Node.js technology.

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