Develop Reference

boolean does not change in function JavaScript

I have the following code:
const ships = (length) => {
isSunk = false
console.log('BEFORE: ' + isSunk)
const shipSize = length
let hits = []
const hitLocation = location => {
hits.push(location);
isSunk = true;
console.log('INSIDE: ' + isSunk)
}
console.log('AFTER: ' + isSunk)
return {
isSunk,
hitLocation,
hits,
shipSize
}
}
const two = ships(2)
two.hitLocation(1)
two.hitLocation(2)
console.log('FINAL: ' + two.isSunk)
console.log('HITS: ' + two.hits)
Is there a reason why isSunk is not saved as true when I call it in the end?
Is it due to the nested functions?

When you set the boolean into the object, it is that value. It is not a reference to the variable. So when you change the variable, the value you saved inside of the object that you returned is not updated.
You can use a function to get the value
const ships = (length) => {
isSunk = false
console.log('BEFORE: ' + isSunk)
const shipSize = length
let hits = []
const hitLocation = location => {
hits.push(location);
isSunk = true;
console.log('INSIDE: ' + isSunk)
}
console.log('AFTER: ' + isSunk)
return {
isSunk: () => isSunk,
hitLocation,
hits,
shipSize
}
}
const two = ships(2)
two.hitLocation(1)
two.hitLocation(2)
console.log('FINAL: ' + two.isSunk())
Other option is to use a class.
class Ship {
hits = [];
constructor(length) {
this.shipSize = length;
}
get isSunk() {
return this.hits.length === this.shipSize;
}
hitLocation (location) {
this.hits.push(location);
console.log('INSIDE: ' + this.isSunk)
}
}
const two = new Ship(2)
two.hitLocation(1)
two.hitLocation(2)
console.log('FINAL: ' + two.isSunk)

The reason this happens is that isSunk is just a local variable and a value in contrast to hits which is also a local variable but an array and thus just a reference not a value.
As you return the object when calling ship() these values and the reference get returned in an object.
Now when you call hitLocation() it uses the local variable hits to add an entry to the array and as the array is just a reference the local variable hits and the hits in the two object have the same reference so they point to the same memory location, thus the update can be seen using the returned object.
On the other hand hitLocation() also modifies the local variable isSunk but as you do not return that and it is not a reference the object stored in variable two is not updated.
The best way to fix this to my mind is using a class instead of a object here. This will be much more concise and clear than returning and/or passing the object you want to perform some action on to a function all the time.

Unhandled rejection SequelizeDatabaseError when passing dynamic query in where clause

I am trying to decompose a user's get request and put it in a variable named query. then pass the var query into the sequelize's findAll method using it's where clause, it seems like Sequelize thinks i am looking for a table CALLED query when in reality i am trying to pass the object. I'm sorry if i can not explain very well, but here is the code and the error:
var info = [];
//link example: localhost:8081/filter/?descripiton=san+francisco&houseType=house&numOfBedroom=3&numOfBathroom=2&houseSize=500&price=1200
exports.filterListings = function(req) {
//create an object literal which we will return, and has a nested object named filteredList inside.
//filteredList contains an array named listings where we will put listings that match our filter inside
let response = {
filteredList: {listings: []},
};
//now we need to see how the user wants us to filter the listings
const query = req.query;
//do some logic where we decompose query
if(query.descripiton != undefined) {
//info = info + 'descripiton: ' + query.descripiton+', ';
info.push('descripiton: ' + query.descripiton+', ');
console.log(info);
}
if(query.houseType != undefined) {
//info = info + 'houseType: ' + query.houseType+', ';
info.push('houseType: ' + query.houseType+', ');
//console.log(info);
}
if(query.numOfBedroom != undefined) {
//info = info + 'numOfBedroom: ' + query.numOfBedroom+', ';
info.push('numOfBedroom: ' + query.numOfBedroom+', ');
}
if(query.numOfBathroom != undefined) {
//info = info + 'numOfBathroom: ' + query.numOfBathroom+', ';
info.push('numOfBathroom: ' + query.numOfBathroom+', ');
}
if(query.houseSize != undefined) {
//info = info + 'houseSize: ' + query.houseSize+', ';
info.push('houseSize: ' + query.houseSize+', ');
}
if(query.price != undefined) {
//info = info + 'price: ' + query.price;
info.push('price: ' + query.price);
}
and then when i try to pass the info variable
listingModel.findAll({
//error because it wont recognize the variable search nor will it recognize info
where: {info}
}).then(listings => {
// so we loop through listings and insert what we have found into the response (which we are going to return)
for(var i = 0; i < listings.length; i++) {
response.filteredList.listings.push(listings[i]);
}; // loop where we insert data into response done
I want it to find all listings based on the dynamic query but i am getting the error:
Unhandled rejection SequelizeDatabaseError: Unknown column 'Listing.info' in 'where clause'
Thank you very much for the potential help!

Let's try to sort through your problems one by one. Sorry for the pun :p
Instead of using multiple if for creating your filtered list. Use for ... in. Then use that array of objects along with Sequelize.Op to create your query.
Example:
const Op = require('sequelize').Op;
const whereClause = [];
const query = req.query;
for(const key in query) {
if(query[key] !== '' && query[key] !== null) {
//object will be pushed to the array like "houseType:big"
whereClause.push({key:query[key]})
}
}
//you now have the where clause
//use it in your query with Op.and
listingModel.findAll({
where: {
[Op.and]: whereClause,
}
});
More info about querying with Sequelize - Operators

DOM view does not get updated, angular is not in zone

I have a zone related problem, and i can't get it working. i'm new to angular but have some basic javascript understanding.
So what is the problem, i can not get the view updated.
Im using a third party library for ionic BLE, and use this in a provider
providers/communication-controller.ts
set_ble_tolisten(){
//subscribe to receive notification, rx channel
console.log(' set_ble_tolisten' + NgZone.isInAngularZone());
this.ble.startNotification(this.peripheral_object.id,
this.TRANSPARANT_SERVICE, this.TX_CHARACTERISTIC).subscribe(
(data) => this.handlereceiveddata(data),
() => console.log('Unexpected Error', 'Failed to subscribe for
temperature changes')
)
}
ble_communication_controller(port,command,payload,payloadsize,
callback)
{
//create buffer
var BLE_Sendbuffer= new Int8Array(payloadsize+10);
var package_index = 0;
this.generatePacketID();
this.ble_send_que.push({
"packetid" : this.packetid,
"action" : callback
});
//Generate send message
BLE_Sendbuffer[ some data]
//send message
this.ble.write(this.peripheral_object.id,this.TRANSPARANT_SERVICE,
this.RX_CHARACTERISTIC,BLE_Sendbuffer.buffer).then(
() => console.log('ble message send'),
e => console.log('ble oops')
);
}
handlereceiveddata(buffer:ArrayBuffer){
var int8View = new Int8Array(buffer);
var ReceivedPacketID = 0;
console.log('handlereceiveddata ' + NgZone.isInAngularZone());
//first check the header
if( ((int8View[0] * 0x100) + int8View[1]) === this.HEADER)
{
//retrieve packetid from received packet
ReceivedPacketID = ((int8View[2] * 0x100) + int8View[3]);
if(ReceivedPacketID === 0) {
console.log('orgin io or rs232');
} else {
//find function based on packetid, and execute
let index_findresult = this.ble_send_que.findIndex(value =>
value.packetid === ReceivedPacketID);
if(index_findresult != -1)
{
this.ble_send_que[index_findresult].action(int8View);
}
//remove object from array
this.ble_send_que.splice(index_findresult, 1);
}
}
set_ble_tolisten() is called to subcribe on the promise.When data is received handlereceiveddata() is called.
To transmit data ble_communication_controller() is called, this function accepts a callback, which is stored. When the ble device response, the handlereceivedata() is called. This then call the callback which is stored a the ble_communication_controller() call
I created a page, configuration, this contains a ts a html and scss file
the configuration.ts
ionViewDidEnter() {
this.communicationController.set_ble_tolisten();
this.sync_device_gui('IO-1');
}
sync_device_gui(port){
console.log('call in zone ' + NgZone.isInAngularZone());
var io_port = 0;
if(port === ‘IO-1')
{
io_port = 0x05;
}
if(port === 'IO-2')
{
io_port = 0x06;
}
this.communicationController.ble_communication_controller(io_port,
GET_IO_STATE,0x00,0,this.update_state_gui);
}
update_state_gui(data){
//rule below added as explained in first comment (location ngzone.run).
this.zone.run(() => {
console.log('repsonse in zone ' + NgZone.isInAngularZone());
console.log('io port state ' + data);
console.log('repsonse in zone ' + NgZone.isInAngularZone());
if(data[8] == 0){
this.relay_1_toggle = true;
this.relay_2_toggle = true;
console.log('state is false set :'+ this.relay_1_toggle + '
state :' + this.relay_2_toggle );
}
if(data[8] == 1){
this.relay_1_toggle = false;
this.relay_2_toggle = false;
console.log('state is true set :'+ this.relay_1_toggle + '
state :' + this.relay_2_toggle );
}
//rule below added as explained in first comment.(location ngzone.run).
});
//ruke below added as explained in first commen. (location markForCheck())
this.cd.markForCheck();
}
when the page is loaded, ionViewDidEnter is called, the problem is that update_state_gui is called from the provider. the data receives in this function. isInAngularZone, tells me that it is false, out of zone. The
relay_1_toggle and relay_2_toggle are toggle button in html.
And the get not updated, i tried ngzone.run or a timeout and markForCheck(). but it does not work.
Thanks for your help

javascript Firebase how to fire 'value' events in sequence?

I have a function firing two 'value' Firebase events. One is necessary to get the number of children, which is corresponding to the deepest path of the next one.
function myFunction(data){
//get last child
var lastchild = 0;
var data_child = firebase.database().ref('rooms/' + 633 + '/' + 630);
data_child.once('value', function(child) {
if(child.exists()){
lastchild = child.numChildren();
console.log('function 1');
}else{
console.log('error no child');
}
});
//use this number to read the path
var msgsStored = firebase.database().ref('rooms/' + 633 + '/' + 630 + '/' + lastchild);
msgsStored.orderByChild('datetime').once('value', function(snapshot) {
var store = (snapshot.val());
snapshot.forEach(function(child) {
console.log('function 2');
//do something
}
}
}//myFunction
Firebase will always fire the last 'value' event before the first one. Why?
That will result always on variable lastchild = 0; and 'function 2' will always print before 'function 1' on console.
I tried also creating a callback(); function to try control the order with JavaScript, but will not work.
I know different events of Firebase are fired in different order, but in my case I need to read stored data only.
Anybody knows what am I missing and how to address me to a solution?

Firebase, like most of the modern web, reads data from its database asynchronously. This is easiest to see by placing some log statements in your code:
console.log("1");
var data_child = firebase.database().ref('rooms/' + 633 + '/' + 630);
data_child.once('value', function(child) {
console.log("2");
});
console.log("3");
The output of this is:
1
3
2
This is probably not what you initially expected, but explains a lot on the behavior you're seeing. When log statement 3 executes, the data from the first listener hasn't been loaded yet. So you can't make a query based on that data.
For this reason you always need to move the code that requires the data into the callback:
var lastchild = 0;
var data_child = firebase.database().ref('rooms/' + 633 + '/' + 630);
data_child.once('value', function(child) {
if(child.exists()){
lastchild = child.numChildren();
//use this number to read the path
var msgsStored = firebase.database().ref('rooms/' + 633 + '/' + 630 + '/' + lastchild);
msgsStored.orderByChild('datetime').once('value', function(snapshot) {
var store = (snapshot.val());
snapshot.forEach(function(child) {
console.log('function 2');
//do something
}
}
}else{
console.log('error no child');
}
});

onResourceReceived logs every resource twice?

I'm trying to use phantomjs to get some metrics about the likelihood of a race condition affecting a page, I have 2 script files, some functionality hosted on my site is dependant on some globals set by a file coming from a third party.
I thought that using onResourceReceived in phantomjs I could log when each file loads and then run that test a bunch of times to get an idea of how often this race condition will cause issues, an example of my code is below (it's not the actual code and I'm not affiliated with the BBC):
(function (p, wp) {
"use strict";
var page, start,
count = 0, max = 10,
webpage = require('webpage'),
url = "http://www.bbc.co.uk";
function process() {
if (max == count) {
console.log('done processing!');
p.exit();
} else {
count++;
start = new Date();
page = wp.create();
page.onResourceReceived = onResourceReceived;
page.open(url, onOpen);
}
}
function onResourceReceived(response) {
var match, t = new Date(),
url = response.url,
status = response.status;
t = t.valueOf() - start.valueOf();
if (!!(match = url.match(/locator\.css/))) {
console.log(match[0] + ': ' + t + 'msecs status: ' + status);
}
if (!!(match = url.match(/en-GB\.json/))) {
console.log(match[0] + ': ' + t + 'msecs status: ' + status);
}
};
function onOpen() {
console.log('Test ' + count + ' done!!!');
page.close();
process();
}
process();
}(phantom, require('webpage')));
This kinda runs how I expected except that each file is logged twice, why is this?
Sometimes the time differences are very different.
locator.css: 323msecs status: 200
locator.css: 323msecs status: 200
en-GB.json: 2199msecs status: 200
en-GB.json: 2200msecs status: 200
Test 1 done!!!

You need to check for response.stage property. stage will have start and end. start gives the first byte arrived time and end give you the when you got the complete response.
please add a check in your function.
function onResourceReceived(response) {
if(response.stage == 'end') return;
//rest of your code from above example.
};