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Start your free trialSamuel Kleos
Front End Web Development Techdegree Student 13,631 PointsBut with .then() you can't pass values as arguments into callbacks like you can with nested callbacks?
See the following code where I've written nested callbacks with continuation-passing style as an alternative to the chained mathPromise.then() methods in the instruction.
function calculate(x, callback) {
callback(x);
}
function add(x, y, callback) {
callback(x + y)
}
function finalValue(nextValue) {
console.log("The final value is ${nextValue}")
}
// Using nested callbacks to pass n
calculate(5, (n) => { // calculate passes callback with n param executing add()
// n param becomes input x and gets added 10
add(n, 10, (n) => { // add passes callback with n param executing subtract()
subtract(n, 2, (n) => {
multiply(n, 5, (n) => {
finalValue(n) ;
});
});
});
});
1 Answer
Steven Parker
231,269 PointsNote that your example is not an alternative to the lesson code as it contains no promises or async operations.
But you can pass values using promises and then by currying the callbacks to include the extra arguments:
const add = (x, y) => x + y;
const subtract = (x, y) => y - x;
const multiply = (x, y) => x * y;
const finalValue = nextValue => console.log(`The final value is ${nextValue}`);
const value = 5;
const mathPromise = new Promise( resolve => { resolve(value); } );
mathPromise
.then(add.bind(this, 10))
.then(subtract.bind(this, 2))
.then(multiply.bind(this, 5))
.then(finalValue);
// The final value is 65
Samuel Kleos
Front End Web Development Techdegree Student 13,631 PointsSamuel Kleos
Front End Web Development Techdegree Student 13,631 PointsFascinating!