Programmatically creating a chained sequence of jQuery promises

Question

I have a function to delete a list an array of files, filePaths, by calling a single deleteFile(filePath) on each of the files in a list (some APIS I\'m using don\'t support

Answer 1

$.when doesn't launch anything, they were launched in your map loop. $.when simply returns a promise for an array of promises.

If you want them sequentially, use reduce:

function deleteFiles(filePaths) {
    return filePaths.reduce(function(cur, next) {
         return cur.then(function() {
             return deleteFile(next);
         });
    }, $().promise());
}

If you want them sequentially, while also getting the array back with respective results:

function deleteFiles(filePaths) {
    var ret = filePaths.slice(0);
    return filePaths.reduce(function(cur, next, i) {
         return cur.then(function() {
             return ret[i] = deleteFile(next);
         });
    }, $().promise()).then(function(){
         return $.when.apply($, ret);
    })
    //These don't make any sense to call in this function but sure
    .then(function(schemas) {
         console.log("DONE", this, schemas);
    }).fail(function(error) {
         console.log("My ajax failed");
    });
}