Nodejs Calling Function From Within A Function

I have 3 methods exports.getImageById = function (resultFn, id) { ... } exports.getCollectionById = function (resultFn, id) { } in the third method I want to call both methods e

Solution 1:

When you call this.getCollectionById passing it a callback, the callback doesn't have access to the same this

The simplest solution is to save this as a local variable.

exports.getCollectionImages = function (resultFn, collectionId) {    
    var arr = newArray();        
    var me = this; // Save thisthis.getCollectionById(   // fine, 1st callfunction (result) {
            var images = result.image;
            for (var i = 0; i < images.length; i++) {
                // Use me instead of this
                me.getImageById(function (result1) {   // error, 2nd call
                    arr[i] = result1;
                }, images[i]);
            }
        }, collectionId);
    resultFn(arr);
}

Solution 2:

The value of this inside the inner function is not the same object as outside, because it's determined depending on how the function is called. You can find a detailed explanation in the MDN article on this.

One of the ways to solve it is by keeping a reference to the outer this in another variable such as that:

var that = this;
this.getCollectionById(   // fine, 1st callfunction (result) {
        var images = result.image;
        for (i = 0; i < images.length; i++) {
            that.getImageById(function (result1) {   // 2nd call
                    arr[i] = result1;
                }, images[i]
            );

        }
    }
    , collectionId
);