Parameters in a callback
1. By calling the callback with arguments inside a function
You pass the callback itself, and the calling function passes it the data it needs.
javascript
function fetchData(callback) {
const data = 'Data from the server';
callback(data); // pass a parameter into the callback
}
function showData(info) {
console.log('Received:', info);
}
fetchData(showData);Output:
javascript
Received: Data from the server2. Through a closure (when you need to "bake in" arguments in advance)
javascript
function processUser(action) {
const user = { name: 'Tim' };
action(user);
}
processUser(user => console.log(`Hello, ${user.name}!`));or:
javascript
function doLater(callback) {
setTimeout(callback, 1000);
}
doLater(() => console.log('In a second!'));Summary: Parameters are passed into a callback the same way as into any function - you just need to call the callback with the needed arguments inside another function.
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