How to show method declaration in NodeJs [closed] - javascript

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is there any way to show function declaration. e.g what it takes as parameters and what it returns in CLI? as like "tinker in laravel"
I searched over internet but found nothing.

I am not sure if I correctly understand your question. To find out what a function looks like, including its parameters (and all its code including what it returns), you can do a (slightly dirty) hack like this:
function a(b,c) {
return b + ", " + c;
}
console.log(a.toString());
Output:
'function b(a,b){return a+" " + b}'
Alternatively, if you are looking for documentation, for most NPM modules and note itself, there is solid API documentation. See https://nodejs.org/api/ for example.

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How to set variable of image src and use in javascript function? [closed]

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So if i have some codes like this
If(sceneA){document.getElementById("divA").src="A.png";}
If(document.getElementById("divC")=="A.png"){document.getElementById("divB").src="B.png";}//And alot of codes here
How can I use a var to shorten strings like
document.getElementById("divA").src="A.png"
document.getElementById("divB").src="B.png"
so i can use them both inside (IF) and {function}
As they have to repeat quite a few times in the codes.
Thanks alot!
That's exactly what functions are for.
Define a function for repeating blocks of code as follows:
function setSrc(divName, imgName){
document.getElementById("div"+divName).src = imgName+".png";
}
function srcEquals(divName, imgName){
return (document.getElementById("div"+divName).src == imgName+".png");
}
Then you can replace your code with this:
if(sceneA){setSrc("A","A");}
if(srcEquals("C", "A")){setSrc("B","B");}

What is an example of a "custom function" and "recursion" [closed]

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I have been asked to show I have used these processes in my program but from looking up the definitions, I don't know what they mean. I am confident my program is complicated enough that it uses these processes, but I don't know exactly what they are. What would be an example of these processes used in javascript?
Unsure what you mean by custom function - but recursion is just a function that calls itself.
Example of recursion
countNumTimesToZero = (myNum, count = 0) => {
if (myNum - 1 === 0) return count + 1;
return countNumTimesToZero(myNum - 1, count + 1);
}

Converting a function to its string representation [closed]

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I know that calling toString on function object would give me the string representation of the function definition like:
function foo() { /*...*/ }.toString(); works fine for me.
But here
function stringifyFn(fn) {
// Support: Chrome 50-51 only
// Creating a new string by adding `' '` at the end, to hack around some bug in Chrome v50/51
// (See https://github.com/angular/angular.js/issues/14487.)
// TODO (gkalpak): Remove workaround when Chrome v52 is released
return Function.prototype.toString.call(fn) + ' ';
}
I see that author has used this pattern in many places, what could be the reasons behind it?

Best approach to Logging in javascript [closed]

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I want to console.log but then turn it off in production without deleting the logs statements.
What are other logging levels and how can i utilise them?
What benefits do logging libraries such as log4js offer?
Place this code in your webpage
if(window.location.hostname=="example.com"){
console.log = function(){
return;
}
}
What it will do is, if the domain name is example.com it will override the console.log functionality and it will print nothing in console.
This way it will also work in your local environment.
var myAPI={isLogged:false};
(function(api){
if(window.location.hostname=="dev.example.com"){
myAPI.isLogged=true;
}
api.log=function(msg,level){
if(!level){level='log'} //can be : warn, info, error, debug or log
if( myAPI.isLogged){
console[level](msg);
}
};
})(myAPI) ;
Then , use :
myAPI.log(new Date()+' This is security check ');
or
myAPI.log(new Date()+' Wrong password ','error');

How to get the final result of javascript? [closed]

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I have an html page with a lot of javascript code, for example the content of a div depends on length of an array :
for (var i = 0; i < movieList.length; i++) {
document.body.appendChild(document.createElement('h2')).appendChild(document.createTextNode('title: ' + movieList[i].title));
var cUL = document.body.appendChild(document.createElement('ul'));
cUL.appendChild(document.createElement('li')).appendChild(document.createTextNode(movieList[i].rating));
cUL.appendChild(document.createElement('li')).appendChild(document.createTextNode(movieList[i].year));
cUL.appendChild(document.createElement('li')).appendChild(document.createTextNode(movieList[i].length));
cUL.appendChild(document.createElement('li')).appendChild(document.createTextNode(movieList[i].isComedy));
cUL.appendChild(document.createElement('li')).appendChild(document.createTextNode('main characters: ' + movieList[i].mainCharacters.join(", ")));
}
I am using these perl LWPx::ParanoidAgent and HTML::TokeParser modules to handle the HTML code but the i want the result of the javascript script
You either need to:
Reverse engineer the JS and apply the changes it would make manually or
Run the HTML and JS through a browser or browser-like tool and read the data from its DOM
There are a number of options for the latter, including WWW::Mechanize::Firefox, WWW::Selenium and Wight.
perhaps https://getfirebug.com/ is what you're looking for. Amongst loads of other things you can view your HTML after JavaScript has altered it.

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