Develop Reference

javascript array function can't be used

below is a piece of js code.When I run it with "node" command. It displays. "notes.filter" is not a function.If I comment "JSON.parse" line. It works. But video tutorial does have this line. So I am quite confused here. Could any one helps here. Thanks a lot.
var addNote = (title, body) => {
var notes = [];
var note = {
title,
body
}
try {
var notesstring = fs.readFileSync('notes-data.json');
notes = JSON.parse(notesstring);
} catch (e) {
}
console.log(Array.isArray(notes));
var duplicateNote = notes.filter((note) => note.title === title);
if (duplicateNote.length === 0) {
notes.push(note);
fs.writeFileSync('notes-data.json', JSON.stringify(note));
}
};

I had the same problem while going through the course but ended up fixing it.
For some reason, I was getting back bad JSON, and so I had to delete the note-data.json file, and then re-run the app. This fixed it for me!

Word add-in: Get whole document but File.getSliceAsync method not returning

I'm creating an Office Add-in and am having trouble with the javascript file.getFileAsync method in Word Online (Word 2013 desktop is fine).
I'm using sample code from github...
https://github.com/OfficeDev/office-js-docs/blob/master/docs/word/get-the-whole-document-from-an-add-in-for-powerpoint-or-word.md
My code looks like this...
function getFile() {
Office.context.document.getFileAsync(Office.FileType.Text,
{ sliceSize: 65536},
function (result) {
if (result.status == Office.AsyncResultStatus.Succeeded) {
// Get the File object from the result.
var myFile = result.value;
var state = {
file: myFile,
counter: 0,
sliceCount: myFile.sliceCount
};
getSlice(state);
}
});
}
function getSlice(state) {
state.file.getSliceAsync(state.counter, function (result) {
if (result.status == Office.AsyncResultStatus.Succeeded) {
sendSlice(result.value, state);
state.file.closeAsync();
}
else if(result.status == 'failed')
state.file.closeAsync();
});
}
Before calling file.getSliceAsync the data looks good - myFile.sliceCount is 1. The result function is never called and no errors are thrown in the console.
Thanks for any help you can provide!

UPDATE: this issue is fixed and live. Please try it again it must work now.
thanks!
---------------- ORIGINAL ANSWER JUST FOR REFERENCE ----------------------------
Yes, there is a regression right now in Word Online preventing the code to run successfully. The specific issue is that the file.getSliceAsync method is never calling the call-back function. This only happens with the TEXT type, if you want to get the docx or pdf this should work ok. This issue will be fixed in a couple of weeks.
You have an alternative if you want to get the text of the document you can use the new APIs for Word check out this sample:
Word.run(function(context) {
var myBody = context.document.body;
context.load(myBody);
return context.sync()
.then(function(){
console.log(myBody.text);
});
});
Hope this helps!
Thanks for reporting this issue!
Juan.

node.js - pngjs error: "Stream not writable" randomly

I am working with pngjs through many of it's methods. Most of the time, they work fine. However, like in the following example, I get an error: "Stream is not writable"
var fs = require('fs'),
PNG = require('pngjs').PNG;
var dst = new PNG({width: 100, height: 50});
fs.createReadStream('http://1.1m.yt/hry7Eby.png') //download this picture in order to examine the code.
.pipe(new PNG())
.on('parsed', function(data) {
console.log(data);
});
This case is not singular, I get this error on 1 random png image once a day, through all of pngjs methods, and that error obviously crashes my app.
(note: you can't use the http link I gave you with a readStream, you will have to download & rename it and do something like):
fs.createReadStream('1.png')
Thank you for your time and effort.

This seems to be a bug in the library, though I'm wary of saying so as I'm no expert in PNGs. The parser seems to complete while the stream is still writing. It encounters the IEND, and so calls this:
ParserAsync.prototype._finished = function() {
if (this.errord) {
return;
}
if (!this._inflate) {
this.emit('error', 'No Inflate block');
}
else {
// no more data to inflate
this._inflate.end();
}
this.destroySoon();
};
If you comment out the this.destroySoon(); it finishes the image correctly, instead of eventually calling this function:
ChunkStream.prototype.end = function(data, encoding) {
if (data) {
this.write(data, encoding);
}
this.writable = false;
// already destroyed
if (!this._buffers) {
return;
}
// enqueue or handle end
if (this._buffers.length === 0) {
this._end();
}
else {
this._buffers.push(null);
this._process();
}
};
...which would otherwise end up setting the stream.writeable to false, or, if you comment that out, to pushing a null value into the _buffers array and screwing up the ChunkStream._processRead.
I'm fairly certain this is a synchronicity problem between the time the zlib parser takes to complete and the time the stream takes to complete, since if you do this synchronously it works fine:
var data = fs.readFileSync('pic.png');
var png = PNG.sync.read(data);
var buff = PNG.sync.write(png);
fs.writeFileSync('out2.png', buff);

Instagram API - paging through 'new' posts

So I'm using node.js and the module instagram-node-lib to download metadata for Instagram posts. I have a couple of hashtags that I want to search for, and I want to download all existing posts (handling request failure during pagination) as well as monitor all new posts.
I have managed to crack the first part - downloading all existing posts and handling failure (I noticed that sometimes the Instagram API would just fail on me, so I've added redundancy to remember the last successful page I downloaded and attempt again from that point). For anyone who is interested, here is my code (note, I use Postgres to save the posts, and I've abbreviated/obfuscated some of the code for ease of reading and for commercial purposes) **apologies for the length of code, but I think this will come in useful to someone:
var db = new (require('./postgres'))
,api = require("instagram-node-lib")
;
var HASHTAGS = ["fluffy", "kittens"] //this is just an example!
,CLIENT_ID = "YOUR_CLIENT_ID"
,CLIENT_SECRET = "YOUR_CLIENT_SECRET"
,HOST = "https://api.instagram.com"
,PORT = 443
,PATH = "/v1/media/popular?client_id=" + CLIENT_ID
;
var hashtagIndex = 0
,settings
;
/**
* Initialise the module for use
*/
exports.initialise = function(){
api.set("client_id", CLIENT_ID);
api.set("client_secret", CLIENT_SECRET);
if( !settings){
settings = {
hashtags: []
}
for( var i in HASHTAGS){
settings.hashtags[i] = {
name: HASHTAGS[i],
maxTagId: null,
minTagId: null,
nextMaxTagId: null,
}
}
}
// console.log(settings);
db.initialiseSettings(); //I haven't included the code for this - basically just loads settings from the database, overwriting the defaults above if they exist, otherwise it creates them using the above object. I store the settings as a JSON object in the DB and parse them on load
execute();
}
function execute(){
var params = {
name: HASHTAGS[hashtagIndex],
complete: function(data, pagination){
var hashtag = settings.hashtags[hashtagIndex];
//from scratch
if( !hashtag.maxTagId){
console.log('Downloading old posts from scratch');
getOldPosts();
}
//still loading old (previously failed)
else if( hashtag.nextMaxTagId){
console.log('Downloading old posts from last saved position');
getOldPosts(hashtag.nextMaxTagId);
}
//new posts only
else {
console.log('Downloading new posts only');
getNewPosts(hashtag.minTagId);
}
},
error: function(msg, obj, caller){
apiError(msg, obj, caller);
}
}
api.tags.info(params);
}
function getOldPosts(maxTagId){
console.log();
var params = {
name: HASHTAGS[hashtagIndex],
count: 100,
max_tag_id: maxTagId || undefined,
complete: function(data, pagination){
console.log(pagination);
var hashtag = settings.hashtags[hashtagIndex];
//reached the end
if( pagination.next_max_tag_id == hashtag.maxTagId){
console.log('Downloaded all posts for #' + HASHTAGS[hashtagIndex]);
hashtag.nextMaxTagId = null; //reset nextMaxTagId - that way next time we execute the script we know to just look for new posts
saveSettings(function(){
next();
}); //Another function I haven't include - just saves the settings object, overwriting what is in the database. Once saved, executes the next() function
}
else {
//from scratch
if( !hashtag.maxTagId){
//these values will be saved once all posts in this batch have been saved. We set these only once, meaning that we have a baseline to compare to - enabling us to determine if we have reached the end of pagination
hashtag.maxTagId = pagination.next_max_tag_id;
hashtag.minTagId = pagination.min_tag_id;
}
//if there is a failure then we know where to start from - this is only saved to the database once the posts are successfully saved to database
hashtag.nextMaxTagId = pagination.next_max_tag_id;
//again, another function not included. saves the posts to database, then updates the settings. Once they have completed we get the next page of data
db.savePosts(data, function(){
saveSettings(function(){
getOldPosts(hashtag.nextMaxTagId);
});
});
}
},
error: function(msg, obj, caller){
apiError(msg, obj, caller);
//keep calm and try again - this is our failure redundancy
execute();
}
}
var posts = api.tags.recent(params);
}
/**
* Still to be completed!
*/
function getNewPosts(minTagId){
}
function next(){
if( hashtagIndex < HASHTAGS.length - 1){
console.log("Moving onto the next hashtag...");
hashtagIndex++;
execute();
}
else {
console.log("All hashtags processed...");
}
}
Ok so here is my dilema about solving the next piece of the puzzle - downloading new posts (in other words, only those new posts that have come into existence since I last downloaded all the posts). Should I use Instagram subscriptions or is there a way to implement paging similar to what I've already used? I'm worried that if I use the former solution then if there is a problem with my server and it goes down for a period of time then I will miss out on some posts. I' worried that if I use the latter solution then it might not be possible to page through the records, because is the Instagram API set up to enable forward paging rather than backward paging?
I've attempted to post questions in the Google Instagram API Developers Group a couple of times and none of my messages seem to be appearing in the forum so I thought I'd resort to trusty stackoverflow

Javascript Variable Sometimes Undefined

I know this question has been asked several times, but I couldn't seem to find a solution that worked for me in any of the previous questions. I have a variable that gets set when my HTML page is done loading, but sometimes when my code tries to access that variable, it says that it is undefined. I'm not sure why, since I believe I am waiting for everything to load properly. This exception seems to happen randomly, as most of the time all the code runs fine. Here's a simplified version of my code:
var globalVar;
function initStuff(filePath) {
// I wait till the HTML page is fully loaded before doing anything
$(document).ready(function(){
var video = document.getElementById("videoElementID");
// My parseFile() function seems to run smoothly
var arrayOfStuff = parseFile(filePath);
if (arrayOfStuff == null) {
console.error("Unable to properly parse the file.");
} else {
setGlobalVariable(arrayOfStuff);
video.addEventListener("play", updateVideoFrame, false);
}
});
}
function setGlobalVariable(arrayOfStuff) {
window.globalVar = arrayOfStuff;
}
function updateVideoFrame() {
// A bunch of other code happens first
// This is the line that fails occasionally, saying
// "window.globalVar[0].aProperty.anArray[0] is undefined"
var test = window.globalVar[0].aProperty.anArray[0].aProperty;
}
The only thing that I can think of that might be causing this problem is some sort of synchronicity issue. I don't see why that would be the case, though. Help please!
Edit:
In case the asynchronicity issue is coming from my parseFile(xmlFile) method, here is what I'm doing there. I thought it couldn't possibly be causing the issue, since I force the method to happen synchronously, but in case I'm wrong, here it is:
function parseKML(xmlFile) {
var arrayOfStuff = new Array();
// Turn the AJAX asynchronicity off for the following GET command
$.ajaxSetup( { async : false } );
// Open the XML file
$.get(xmlFile, {}, function(xml) {
var doc = $("Document", xml);
// Code for parsing the XML file is here
// arrayOfStuff() gets populated here
});
// Once I'm done processing the XML file, I turn asynchronicity back on, since that is AJAX's default state
$.ajaxSetup( { async : true } );
return arrayOfStuff;
}

The first thing you should do in your code is figure out which part of:
window.globalVar[0].aProperty.anArray[0]
is undefined.
Since you have multiple chained property references and array references, it could be many different places in the chain. I'd suggest either set a breakpoint right before your reference it examine what's in it or use several console.log() statement sto output each nested piece of the structure in order to find out where your problem is.
console.log("globalVar = " + globalVar);
console.log("globalVar[0] = " + globalVar[0]);
console.log("globalVar[0].aProperty = " + globalVar[0].aProperty);
console.log("globalVar[0].aProperty.anArray = " + globalVar[0].aProperty.anArray);
console.log("globalVar[0].aProperty.anArray[0] = " + globalVar[0].aProperty.anArray[0]);
If the problem is that globalVar isn't yet set, then you have a timing problem or an initialization problem.
If the problem is that one of the other properties isn't set, then you aren't initializing globalVar with what you think you are.
You may also want to write your code more defensibly so it fails gracefully if some of your data isn't set properly.

You need to use defensive programming.
http://www.javascriptref.com/pdf/ch23_ed2.pdf
Example:
var video = document.getElementById("videoElementID") || 0;
-
if( video && video.addEventListener ){
video.addEventListener("play", updateVideoFrame, false);
}
Here's another version of your code.
window.globalVar = globalVar || [];
function setGlobalVariable(arrayOfStuff) {
window.globalVar = arrayOfStuff;
}
function updateVideoFrame() {
// A bunch of other code happens first
// This is the line that fails occasionally, saying
// "window.globalVar[0].aProperty.anArray[0] is undefined"
if( window.globalVar ){
var g = window.globalVar || [];
var d = (g[0] || {})["aProperty"];
// etc...
}else{
console.error( "test error." );
}
}
function initStuff(filePath) {
// I wait till the HTML page is fully loaded before doing anything
$(document).ready(function () {
var video = $("#videoElementID");
// My parseFile() function seems to run smoothly
var arrayOfStuff = parseFile(filePath) || [];
if (arrayOfStuff == null || video == null ) {
console.error("Unable to properly parse the file.");
} else {
setGlobalVariable(arrayOfStuff);
video.bind("play", updateVideoFrame);
}
});
}