{"id":212,"date":"2019-12-27T03:08:00","date_gmt":"2019-12-27T03:08:00","guid":{"rendered":""},"modified":"2024-09-13T15:04:52","modified_gmt":"2024-09-13T15:04:52","slug":"javascript-how-to-convert-recursive-function-with-callbacks-to-use-promises","status":"publish","type":"post","link":"https:\/\/zofxare.com\/zofxare\/blog\/2019\/12\/27\/javascript-how-to-convert-recursive-function-with-callbacks-to-use-promises\/","title":{"rendered":"JavaScript How To Convert Recursive Function With Callbacks to Use Promises"},"content":{"rendered":"

I updated one of my websites to use JavaScript promises instead of callbacks. It was pretty straightforward, but got a little tricky for a recursive function. Below is how to do the conversion update:<\/p>\n

Recursive callback function:<\/p>\n

<\/pre>\n
\nfunction doSomething(value) {
\n    function callback(result) {
\n        console.log(‘Done ‘ + result);
\n    }
\n   
\n    theRecursiveFunction(value, callback);   
\n}<\/p>\n
function theRecursiveFunction(value, next) {  
\n    if (value> 3) {
\n        console.log(‘Try again ‘ + value);
\n        theRecursiveFunction(value-1, next);
\n    } else {
\n        next(value);
\n    }
\n}<\/p>\n
doSomething(5);<\/p>\n
\nRecursive function with promises:<\/p>\n
<\/pre>\n
\nfunction doSomething(value) {
\n    theRecursiveFunction(value)
\n        .then((result) => {
\n            console.log(‘Done ‘ + result);
\n        });                                   
\n}<\/p>\n
function theRecursiveFunction(value) {
\n    return new Promise((resolve, reject) => {
\n        if (value > 3) {
\n         <\/span>   console.log(‘Try again ‘ + value);
\n                    theRecursiveFunction(value-1)
\n                    .then((result) => {
\n                        resolve(result);
\n                    });
\n        } else {
\n            resolve(value);
\n        }
\n    });
\n}<\/p>\n
doSomething(5);<\/p>\n
\n(paid links)<\/p>\n
Learn JavaScript<\/a><\/p>\n