How do I convert this code to chained promises?

Question

I want to create a JS code to create many nested pages. Here is an example with creating 5 nest pages (5 depth levels)

var self = this;
var parentPageId = 1; // this is initial data. 

// 1
this._genPage(spaceKey, parentPageId).done(function (createdPage) {
    // 2
    self._genPage(spaceKey, createdPage.id).done(function (createdPage) {
        // 3
        self._genPage(spaceKey, createdPage.id).done(function (createdPage) {
            // 4
            self._genPage(spaceKey, createdPage.id).done(function (createdPage) {
                // 5
                self._genPage(spaceKey, createdPage.id).done(function (createdPage) {
                Util.showSuccessMessage('Data Generated: 5 nested pages');
            });
        });
    });
});

How do I convert above code to create any number of nest pages? Currently, I am using jQuery. It is fine if you suggest any Promise library to solve this problem.

Thank you.

[unnest them and chain instead](http://stackoverflow.com/a/22000931/1048572)? — Bergi, May 24 '16 at 10:54

Jamiec · Answer 1 · 2016-05-24T11:06:38.997

2

promises are designed to be chained, what you return from one done is resolved by the next done in the chain:

this._genPage(spaceKey, parentPageId)
    .done(function (createdPage) {
       return self._genPage(spaceKey, createdPage.id);
    }).done(function (createdPage) {
       return self._genPage(spaceKey, createdPage.id);
    }); // etc

Some simple recursion (or even a loop) can be done to make this any number of levels deep.

function genPagesRecursive(spaceKey, id, depth){
   if(depth == 0){
      return 'Data Generated';
   }

   return self._genPage(spaceKey, id).done(function(createdPage){
       return genPagesRecursive(spaceKey,id,--depth);
   })
}

You can even chain another done on the call to the recursive method:

genPagesRecursive(spaceKey, creadtedPage.id, 5).done(function(msg){
     Util.showSuccessMessage(msg);          
});

edited May 24 '16 at 11:06

answered May 24 '16 at 10:59

Jamiec

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Do you mean `return genPagesRecursive(spaceKey,id,--depth)` in your done for the recursive example? – ste2425 May 24 '16 at 11:06
@ste2425 thanks - changed the method name half way through. – Jamiec May 24 '16 at 11:07
I tested and it works like a charm. Thank you @Jamiec. I don't have enough points to vote the answer :( – Tung Dang May 30 '16 at 02:33

score 1 · Answer 2 · answered May 24 '16 at 10:53

Simple recursion will do.

function createNestedPages(spaceKey, parentPageId, numberOfPages) {
  if (numberOfPages <= 0) {
    return;
  }

  this._genPage(spaceKey, parentPageId).done(function (createdPage) {
     createNestedPages(spaceKey, createPage.id, numberOfPages - 1);
  });
}

How do I convert this code to chained promises?

2 Answers2