Develop Reference

JS code generates error in Google Tag Manager

I am trying to add following code in GTM to measure Web Core Vitals
<script type="text/javascript">
new PerformanceObserver((entryList) => {
for (const entry of entrytList.getEntries()) {
const elm = entry.element;
console.log(elm);
}
}).observe({type: 'largest-contentful-paint', buffered:true});
</script>
This code works in Console but when i try to publish it in GTM it generates error message as below
Not sure what is wrong with the code as it should support ECMA16 for GTM

Yes, GTM is pretty slow when it comes to ES6 adoption. It partially adopted it for things like templates, but not fully even there. And obviously it didn't adopt it for custom html tags.
What you'll have to do is rewrite your code to be ES5 compliant. Or you can use babel to do an automated transition. it will look like this:
new PerformanceObserver(function (entryList) {
var _iteratorNormalCompletion = true;
var _didIteratorError = false;
var _iteratorError = undefined;
try {
for (var _iterator = entrytList.getEntries()[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
var entry = _step.value;
var elm = entry.element;
console.log(elm);
}
} catch (err) {
_didIteratorError = true;
_iteratorError = err;
} finally {
try {
if (!_iteratorNormalCompletion && _iterator.return) {
_iterator.return();
}
} finally {
if (_didIteratorError) {
throw _iteratorError;
}
}
}
}).observe({ type: 'largest-contentful-paint', buffered: true });
You probably don't need all the try catch and finally, but babel is being honest with what it does.

JavaScript .startWith() function not working in IE, inside angularjs project

Hi im using Angularjs for my project, There is nationality search drop down. I want to map which is typing on Input and filter it inside nationality JSON object. This part is working fine in other browsers except IE. There is console error "Object doesn't support property or method 'startsWith'". this is my code, Can i know how to add "String.prototype.startsWith" for this issue for my code.
$scope.searchNationality = function (data) {
var output = [];
if (data != "" && data != undefined) {
$scope.ShowNationalityDropDown = true;
for (var i = 0; i < $scope.nationalityList.length; i++) {
if ($scope.nationalityList[i].content.toLowerCase().startsWith(data.toLowerCase())) {
output.push($scope.nationalityList[i]);
}
}
$scope.nationalityListSearchResults = output;
} else {
$scope.ShowNationalityDropDown = false;
$scope.nationalityListSearchResults = [];
}
};

You can try changing from .startsWith to .indexOf since it is compatible with IE for lower versions. If .indexOf returns 0 then the string is in the first position of the string that calls that function, which can be usable when you are in this kind of situation that you can't use .startsWith().
const str = "Hey this is a sample string!"
console.log(str.indexOf("Hey") === 0)
console.log(str.indexOf("sample") === 0)

$scope.searchNationality = function (data) {
var thereIsData = data != "" && data != undefined;
var output = thereIsData
? $scope.nationalityList.filter(function (nationality) {
return nationality.content.toLowerCase().indexOf(data.toLowerCase())) == 0;
})
: [];
$scope.ShowNationalityDropDown = thereIsData;
}

Is there a way to manipulate included JS without eval()?

I know lots of people think "eval is evil," but I have to accomplish something and I'm having trouble figuring out how to do it without eval().
The situation is this: an external file (I have no control over it--EDIT: but it's not user-generated. It's from a trusted source! I imagine this is important) is spitting out JavaScript for me to use. This JavaScript contains some nice JSON data (which is what I need to get), but it's flanked by ordinary JavaScript statements declaring variables and calling functions and such. It looks kinda like this:
var foo = new Object();
foo['KEY'] = {Field1: 'Value1', Field2: 'Value2'};
eval('fooFunction(foo)');
If I eval() this, I can just parse foo['KEY'] and be done with it. The only way I can think to do this without eval() is with a bunch of annoying replace()ments, which hardly seems better. Am I missing some obvious way to do this? Most of the "you don't have to use eval()" alternatives I usually see assume I have complete control over everything, but in this case I have to work around this existing code.
EDIT: I should add that this code is being obtained via an AJAX call from a proxy script (cross-domain stuff), so none of the variables are accessible. If they were, I'd obviously just be able to parse foo['KEY'] and be on my merry.
SECOND EDIT: nothing conclusive yet! I'm getting dangerously close to concluding that eval() is the way to go. Can you stomach this outcome? I'm about to give in to evil(). Somebody stop me, because it's looking like the only way.

The external code better send back valid JSON. The value in your example is not valid JSON, as the keys must be wrapped with double quote.
I came up with small pure JavaScript parser, that can handle simple invalid JSON by adding double quotes by itself. It currently won't support non string values.
function ParseRawJSON(rawCode) {
var arrCandidates = [];
var lastOpenBracketIndex = -1;
for (var i = 0; i < rawCode.length; i++) {
var curChar = rawCode.charAt(i);
if (curChar === "}") {
if (lastOpenBracketIndex >= 0) {
arrCandidates.push(rawCode.substr(lastOpenBracketIndex, i - lastOpenBracketIndex + 1));
lastOpenBracketIndex = -1;
}
} else if (curChar === "{") {
lastOpenBracketIndex = i;
}
}
var arrJsonObjects = [];
for (var i = 0; i < arrCandidates.length; i++) {
var currentJSON = null;
try {
currentJSON = JSON.parse(arrCandidates[i]);
} catch (e) {
//try fixing
var fixedCandidate = TryFixJSON(arrCandidates[i]);
if (fixedCandidate) {
try {
currentJSON = JSON.parse(fixedCandidate);
} catch (e) {
currentJSON = null;
}
}
}
if (currentJSON != null) {
var keys = [];
for (var key in currentJSON)
keys.push(key);
if (keys.length > 0)
arrJsonObjects.push(currentJSON);
}
}
return arrJsonObjects;
function Trim(s, c) {
if (c instanceof Array) {
for (var i = 0; i < c.length; i++)
s = Trim(s, c[i]);
return s;
}
if (typeof c === "undefined")
c = " ";
while (s.length > 0 && s.charAt(0) === c)
s = s.substr(1, s.length - 1);
while (s.length > 0 && s.charAt(s.length - 1) === c)
s = s.substr(0, s.length - 1);
return s;
}
function TryFixJSON(strBlock) {
if (strBlock.indexOf(":") <= 0)
return false;
strBlock = strBlock.replace("{", "").replace("}", "");
var mainParts = strBlock.split(",");
for (var i = 0; i < mainParts.length; i++) {
var currentPart = Trim(mainParts[i]);
if (currentPart.indexOf(":") <= 0)
return false;
var subParts = currentPart.split(":");
if (subParts.length !== 2)
return false;
var currentKey = Trim(subParts[0], [" ", "'", "\""]);
var currentValue = Trim(subParts[1], [" ", "'", "\""]);
if (currentKey.length === 0)
return false;
subParts[0] = "\"" + currentKey + "\"";
subParts[1] = "\"" + currentValue + "\"";
mainParts[i] = subParts.join(":");
}
return "{" + mainParts.join(", ") + "}";
}
}
This will just look for anything between { and } and try to parse as JSON. No eval, in case of failure it'll just ignore the invalid block. Success? Great, it will return plain array of the valid JSON's it found.
Usage example:
var rawCode = "var foo = new Object(); { dummy here }}} function boo() {}" +
"foo['KEY'] = { \"Field1\": \"Value1\", \"Field2\": \"Value2\"}; hello {\"foo\": \"bar\"} and it's over ";
var jsonObjects = ParseRawJSON(rawCode);
for (var i = 0; i < jsonObjects.length; i++) {
for (var key in jsonObjects[i]) {
var value = jsonObjects[i][key];
//got key and value...
}
}
Live test case, using fixed version of your sample code.

A generally safer alternative to using eval is creating a new Function and passing it the string function body. That way (unless something is explicitly acessing the window object) you won't have access to the global scope and can keep it encapsulated in the function scope.
Let's say the first two lines of your example code are the JavaScript that you'd like to evaluate, if you know the name of the variable you want to retrieve as a JSON object you can just return it at the end of the created function and then call it:
var js = "var foo = {}; foo['KEY'] = {Field1: 'Value1', Field2: 'Value2'};";
var fn = new Function(js + ';return foo;');
var result = fn();
console.log(JSON.stringify(result));
This is also what MDN suggests doing in the documentation for eval:
More importantly, third party code can see the scope in which eval() was invoked, which can lead to possible attacks in ways of which the similar Function is not susceptible.

If the JSON contains just data and not functions you can use JSON.parse()
See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse for more detailed info.

As the method has been placed in to the global, then you can do
window["fooFunction"](foo)

SWF Object library will work in all the browsers?

if (typeof t.plugins != D && typeof t.plugins[S] == r) {
ab = t.plugins[S].description;
if (ab && !(typeof t.mimeTypes != D && t.mimeTypes[q] && !t.mimeTypes[q].enabledPlugin)) {
T = true;
X = false;
ab = ab.replace(/^.*\s+(\S+\s+\S+$)/, "$1");
ag[0] = parseInt(ab.replace(/^(.*)\..*$/, "$1"), 10);
ag[1] = parseInt(ab.replace(/^.*\.(.*)\s.*$/, "$1"), 10);
ag[2] = /[a-zA-Z]/.test(ab) ? parseInt(ab.replace(/^.*[a-zA-Z]+(.*)$/, "$1"), 10) : 0
}
} else {
if (typeof O.ActiveXObject != D) {
try {
var ad = new ActiveXObject(W);
if (ad) {
ab = ad.GetVariable("$version");
if (ab) {
X = true;
ab = ab.split(" ")[1].split(",");
ag = [parseInt(ab[0], 10), parseInt(ab[1], 10), parseInt(ab[2], 10)]
}
}
} catch (Z) {}
}
}
return {
w3: aa,
pv: ag,
wk: af,
ie: X,
win: ae,
mac: ac
}
}()
The above code used in swf object library .They checking plugin and ActiveX object written in jquery.Activex will work in IE only.My doubt is whether it will work in all the browsers?if it is yes means ,how its working?

Why shouldn't it work? The check for ActiveX is conditional as well as the access to the ActiveX object catched in case of an error.
So any browser that does not support non-IE behavior (that is, all except IE ;)), will be handled by the else.
BTW: the latest version in the repos has the code a little differently structrued
.... }
else if (typeof win.ActiveXObject != UNDEF) {
try {
var a = new ActiveXObject(SHOCKWAVE_FLASH_AX);
if (a) { // a will return null when ActiveX is disabled
d = a.GetVariable("$version");
if (d) {
ie = true; // cascaded feature detection for Internet Explorer
d = d.split(" ")[1].split(",");
playerVersion = [parseInt(d[0], 10), parseInt(d[1], 10), parseInt(d[2], 10)];
}
}
catch(e) {}
}
It's not an else anymore but an else if (again with a try-catch). The most common case is coverd before hand. They simply check for all the plugins loaded by the browser as reported by navigator.plugins. Since this is the way to do it, most browsers will never enter the else if part.
To get some information about navigator.plugins, check the MDN docs. This is a browser thing and available in all browsers (except the usual IEs, but the technique from the code above will take care of this). This will always be "plugins". If you try to access it differently e.g. "plugin", you will get an error since it is not defined.
I'm not quite sure what you mean by mentioning jQuery. This is vanilla JS, so there is no jQuery used. We used this library quite often and I can asure you, it is stable and well tested.

Windows Scripting to call other commands?

I was trying my hand at Windows shell scripting using cscript and Javascript. The idea was to take a really long Python command that I was tired of typing into the command line over and over. What I wanted to do was write a script that is much shorter to write the whole Python command into a Windows script and just call the Windows script, which would be a lot less to type. I just don't know how I would go about calling a "command within a command" if that makes sense.
This is probably an easy thing, but I'm an newbie at this so please bear with me!
The idea:
Example original command: python do <something really complicated with a long filepath>
Windows Script: cscript easycommand
<package id = "easycommand">
<job id = "main" >
<script type="text/javascript">
// WHAT GOES HERE TO CALL python do <something really complicated>
WScript.Echo("Success!");
</script>
</job>
</package>
Thanks for all your help!

Here's what I use
function logMessage(msg) {
if (typeof wantLogging != "undefined" && wantLogging) {
WScript.Echo(msg);
}
}
// http://msdn.microsoft.com/en-us/library/d5fk67ky(VS.85).aspx
var windowStyle = {
hidden : 0,
minimized : 1,
maximized : 2
};
// http://msdn.microsoft.com/en-us/library/a72y2t1c(v=VS.85).aspx
var specialFolders = {
windowsFolder : 0,
systemFolder : 1,
temporaryFolder : 2
};
function runShellCmd(command, deleteOutput) {
deleteOutput = deleteOutput || false;
logMessage("RunAppCmd("+command+") ENTER");
var shell = new ActiveXObject("WScript.Shell"),
fso = new ActiveXObject("Scripting.FileSystemObject"),
tmpdir = fso.GetSpecialFolder(specialFolders.temporaryFolder),
tmpFileName = fso.BuildPath(tmpdir, fso.GetTempName()),
rc;
logMessage("shell.Run("+command+")");
// use cmd.exe to redirect the output
rc = shell.Run("%comspec% /c " + command + "> " + tmpFileName,
windowStyle.Hidden, true);
logMessage("shell.Run rc = " + rc);
if (deleteOutput) {
fso.DeleteFile(tmpFileName);
}
return {
rc : rc,
outputfile : (deleteOutput) ? null : tmpFileName
};
}
Here's an example of how to use the above to list the Sites defined in IIS with Appcmd.exe:
var
fso = new ActiveXObject("Scripting.FileSystemObject"),
windir = fso.GetSpecialFolder(specialFolders.WindowsFolder),
r = runShellCmd("%windir%\\system32\\inetsrv\\appcmd.exe list sites");
if (r.rc !== 0) {
// 0x80004005 == E_FAIL
throw {error: "ApplicationException",
message: "shell.run returned nonzero rc ("+r.rc+")",
code: 0x80004005};
}
// results are in r.outputfile
var
textStream = fso.OpenTextFile(r.outputfile, OpenMode.ForReading),
sites = [], item,
re = new RegExp('^SITE "([^"]+)" \\((.+)\\) *$'),
parseOneLine = function(oneLine) {
// each line is like this: APP "kjsksj" (dkjsdkjd)
var tokens = re.exec(oneLine), parts;
if (tokens === null) {
return null;
}
// return the object describing the website
return {
name : tokens[1]
};
};
// Read from the file and parse the results.
while (!textStream.AtEndOfStream) {
item = parseOneLine(textStream.ReadLine()); // you create this...
logMessage(" site: " + item.name);
sites.push(item);
}
textStream.Close();
fso.DeleteFile(r.outputfile);

Well, basically:
Obtain a handle to the shell so you can execute your script
Create the command you want to execute (parameters and all) as a string
Call the Run method on the shell handle, and figure out which window mode you want and also whether you want to wait until the spawned process finishes (probably) or not.
Error handling because Run throws exceptions
At this point it's worth writing a lot of utility functions if ever you need to do it more than once:
// run a command, call: run('C:\Python27\python.exe', 'path/to/script.py', 'arg1', 'arg2') etc.
function run() {
try {
var cmd = "\"" + arguments[0] + "\"";
var arg;
for(var i=1; i< arguments.length; ++i) {
arg = "" + arguments[i];
if(arg.length > 0) {
cmd += arg.charAt(0) == "/" ? (" " + arg) : (" \"" + arg + "\"");
}
}
return getShell().Run(cmd, 1, true); // show window, wait until done
}
catch(oops) {
WScript.Echo("Error: unable to execute shell command:\n"+cmd+
"\nInside directory:\n" + pwd()+
"\nReason:\n"+err_message(oops)+
"\nThis script will exit.");
exit(121);
}
}
// utility which makes an attempt at retrieving error messages from JScript exceptions
function err_message(err_object) {
if(typeof(err_object.message) != 'undefined') {
return err_object.message;
}
if(typeof(err_object.description) != 'undefined') {
return err_object.description;
}
return err_object.name;
}
// don't create new Shell objects each time you call run()
function getShell() {
var sh = WScript.CreateObject("WScript.Shell");
getShell = function() {
return sh;
};
return getShell();
}
For your use case this may be sufficient, but you might want to extend this with routines to change working directory and so on.