Develop Reference

Having problems with Javascript Else If statement in Node Red

I have been fighting this problem all day. Heres a snippet of my code, 5 lines down in the else if is where things get screwy. I am also new to Javascript so that may be the reason I am unable to spot the mistake, but from what I have seen elsewhere, this code should work. Also the comments on lines 5 and 6 are swapped.
if (msg.payload.License_Plate !== null) {
// This portion checks for a valid number plate
if (readlpr == dblpr); { // we have a direct match, open the gate
opengate = 1; // will send open signal to gpio
} else if(readlpr !== null); { // from here on, we are checking for a partial plate match
validdigits = 0; // make sure we have data before continuing, as may be a rfid match
{
if (!context.count); { // check to see if counter already used, if not initialise it
context.count = 0;
Image of error message

You have a few errors:
if (readlpr == dblpr); {
...
} else if(readlpr !== null); {
...
if (!context.count); {
And also an extra opening-brace.
These shouldn't have a semi colon on the end:
if (readlpr == dblpr) {
...
} else if(readlpr !== null) {
...
if (!context.count) {
In the end it should look something like this:
if (msg.payload.License_Plate !== null) {
if (readlpr == dblpr) {
opengate = 1;
} else if(readlpr !== null) {
validdigits = 0;
// { <!-- Remove this as well, it's an extra brace
if (!context.count) {
context.count = 0;

Is there a better way to 'do nothing' in javascript if statement?

My url looks like this = https://studentscafe.com/menu/2
I'm trying to check whether or not it has 2 different url params...
1.) ?dinner=1
or
2.) &dinner=1
If #1 is present, do nothing
If #2 is present, do nothing
But if neither are present, default to adding ?dinner=1 to the url.
Is there a better way to have a default do nothing in an if statement? Fiddle here for example.
var path = 'https://studentscafe.com/menu/2';
if (path.indexOf('?dinner=1') >= 1) {
console.log('has ?');
// do nothing leave url as it is
} else {
console.log('does not have ?');
if (path.indexOf('&dinner=1') >= 1) {
// do nothing leave url as it is
} else {
path = path + '?dinner=1';
}
}
Expected output: if the url doesn't have #1 or #2: https://studentscafe.com/menu/2?dinner=1

Instead of
if (something) {
// do nothing
} else {
// do what you need
}
You can use
if (!something) {
// do what you need
}
In your case:
if (path.indexOf('?dinner=1') == -1 && path.indexOf('&dinner=1') == -1) {
path = path + '?dinner=1';
}

Using a regular expression and the ! negation operator, this can be rather simple:
var path = 'https://studentscafe.com/menu/2';
if (!/[?&]dinner=1/.test(path)) {
path += '?dinner=1';
}
console.log(path);

You can do this way.
var path = 'https://studentscafe.com/menu/2';
// Since there is no change to path if it contains either ?dinner=1 or &dinner=1
if (path.indexOf('dinner=1') >= 1) {
console.log('has dinner');
// do nothing leave url as it is
} else {
path = path + '?dinner=1';
}

In modern JS you may simply do like
['?dinner=1','?dinner=2'].every(s => !path.includes(s)) && (path += '?dinner=1');

Unexpected token operator «=», expected punc «,»

i am getting the following error
Parse error: Unexpected token operator «=», expected punc «,» Line
159, column 26
This is my code
function fitBounds(type="all", shape=null) {
var bounds = new google.maps.LatLngBounds();
if ( type == "all" ){
if ((circles.length > 0) | (polygons.length > 0)){
$.each(circles, function(index, circle){
bounds.union(circle.getBounds());
});
$.each(polygons, function(index, polygon){
polygon.getPath().getArray().forEach(function(latLng){
bounds.extend(latLng);
});
});
}
}
else if ( (type == "single") && (shape != null) ) {
if (shape.type == google.maps.drawing.OverlayType.MARKER) {
marker_index = markers.indexOf(shape);
bounds.union(circles[marker_index].getBounds());
}
else {
shape.getPath().getArray().forEach(function(latLng){
bounds.extend(latLng);
});
}
}
if (bounds.isEmpty() != true)
{
map.fitBounds(bounds);
}
}

You are trying to use Default parameters, which are a bleeding edge feature of JavaScript with limited support.
JS Lint rejects them unless you turn on the ES6 option.

#Quentin is exactly right: You need the es6 option.
There's lots more that fails JSLint, however, particularly your use of ==, which is a "coercing operator" -- check JSLint on equality -- and the bitwise option in the jslint section (there's no link directly to jslint directives, I don't think, so I linked just above it). As #AxelH suggests, there's likely more you really want to ask us. ;^)
Here's a version that lints on JSLint.com as it stands today. Note the /*jslint directive line at the top that includes the es6 tag:
/*jslint es6, white, browser */
/*global google, $ */
// These weren't declared, so I'm assuming they're
// within scope in your snippet's context.
// I put others that felt like globals (google, $)
// into globals, above.
var marker_index;
var markers;
var circles;
var polygons;
var map;
function fitBounds(type="all", shape=null) {
var bounds = new google.maps.LatLngBounds();
if ( type === "all" ){
// not sure why you're using bitwise `|` here.
// I think this'll be equivalent, though you should
// be able to set `bitwise` as an option if it's not.
// Still, you're evaluating to booleans, so `|` doesn't
// seem appropriate here.
if ((circles.length > 0) || (polygons.length > 0)){
$.each(circles, function(ignore, circle){
bounds.union(circle.getBounds());
});
$.each(polygons, function(ignore, polygon){
polygon.getPath().getArray().forEach(function(latLng){
bounds.extend(latLng);
});
});
}
}
else if ( (type === "single") && (shape !== null) ) {
if (shape.type === google.maps.drawing.OverlayType.MARKER) {
marker_index = markers.indexOf(shape);
bounds.union(circles[marker_index].getBounds());
}
else {
shape.getPath().getArray().forEach(function(latLng){
bounds.extend(latLng);
});
}
}
if (!bounds.isEmpty())
{
map.fitBounds(bounds);
}
}

#Quentin is right with his answer. You get syntax error due to reasons that he mentioned. What I can add to it is that you might try to drop EC6 syntax, and rewrite your function to old good JS.
// change from
function fitBounds(type="all", shape=null)
// change to
function fitBounds(type="all", shape)

A workaround to this issue could be this:
function fitBounds(type, shape_aux) {
var bounds = new google.maps.LatLngBounds();
if(typeof type === "undefined") {
type = "all";
}
if(typeof shape_aux !== undefined) {
shape = shape_aux;
} else {
shape = null;
}
if ( type == "all" ){
if ((circles.length > 0) | (polygons.length > 0)){
$.each(circles, function(index, circle){
bounds.union(circle.getBounds());
});
$.each(polygons, function(index, polygon){
polygon.getPath().getArray().forEach(function(latLng){
bounds.extend(latLng);
});
});
}
}
else if ( (type == "single") && (shape != null) ) {
if (shape.type == google.maps.drawing.OverlayType.MARKER) {
marker_index = markers.indexOf(shape);
bounds.union(circles[marker_index].getBounds());
}
else {
shape.getPath().getArray().forEach(function(latLng){
bounds.extend(latLng);
});
}
}
if (bounds.isEmpty() != true)
{
map.fitBounds(bounds);
}
}

IE - "Error: Object doesn't support this action"

I'm getting a frustrating javascript error in IE7 that I can't get around. It is working fine in Chrome and Firefox, but not in IE..
The line I am getting the error in is: item = listGetAt(list,'1','-');
This is calling the following custom method:
function listGetAt(list,position,delimiter) {
if(delimiter == null) { delimiter = '-'; }
list = list.split(delimiter);
if(list.length > position) {
return list[position];
} else {
return list.length;
}
}
Can anyone see something I can't?
Many thanks in advance for any help.
Jason

Poor code
Why pass a string as a numeric parameter?
I would consider
function listGetAt(list,position,delimiter) {
delimiter = delimiter || '-';
if (list.indexOf(delimiter) ==-1) return -1;
list = list.split(delimiter);
return list.length>=position?list[position]:null;
}

Javascript switch statement with wildcard?

If my javascript ajaxes away to my server and returns an ID of 49 in the plain text format of [49] is there a way in which i an do something like this... (i have tested and doesnt work)
switch(data)
{
case '[*]':
(..etc.)
break;
}
Where the wildcard is the * and i want to make sure it is enclosed within two square parenthesis?
Because i need to check that there wasnt another word returned like error and i am reserving the default for unexpected errors, any ideas? :) Thanks!

You can do a switch on true explicitely, which will use evaluation on each case statement.
switch (true) {
case ((/^\[\d+\]$/).test(data)):
//matches data;
break;
case (data == "something else"):
//...
break;
default:
//...
}
However, if you have less than say 4-5 cases, it would be better to use if/else if/else if/else blocks.
if ((/^\[\d+\]$/).test(data)) {
//matches data;
} else if (data == "something else") {
//...
} else {
//...
}
I usually do some error trapping in my response methods for service/rest calls so that I almost always return a proper json with an error property if there is an error.
try {
if (response.responseText.indexOf("<html") >= 0) {
throw response.responseText;
}
var data = JSON.parse(response.responseText);
if (data.error)
throw data.error;
//handle response data object.
if ((/^\[\d+\]$/).test(data)) {
//matches data;
} else if (data == "something else") {
//...
} else {
//...
}
} catch(err) {
if (err && err.message) {
//use err.message
} else if (err && err.toString().indexOf("<html") >= 0) {
//handle error text
}
}

You could create a list of patterns and associated callbacks and do a simple loop and check for matches. For example:
var patterns = [];
function myCallback(){ document.write('myCallback!'); }
function myOtherCallback(){ document.write('myOtherCallback!'); }
function myLastCallback(){ document.write('You will never see me!'); }
patterns.push({'pattern':new RegExp(/\[.+\]/),'callback': myCallback});
patterns.push({'pattern':new RegExp(/.+/),'callback':myOtherCallback});
patterns.push({'pattern':new RegExp(/A-Z{3}/),'callback':myLastCallback});
var f = "[49]";
for(var i=0;i<patterns.length;i++){
if(patterns[i].pattern.test(f)){
patterns[i].callback();
}
}
Which outputs the following:
myCallback!myOtherCallback!

You could try to use if else and regex for matching wildcard patterns.
Assuming data = "[49]"; or any digits inside brackets.
if(/\[\d+\]/.test(data)){
//do something
}else{
//default
}

Short answer: No, switch/case can't handle wildcard.
You should probably do some preprocessing/sanity checking before entering the switch, or simply discard it completely since it's more appropriate for specific case scenarios rather than processing streamlined data. Regexp will serve you better here.