How do I check if a variable is an array in JavaScript? if (variable.constructor == Array) 2 25 There are several ways of checking if an variable is an array or not. The best solution is the one you have chosen. variable.constructor === Array This is the fastest method on Chrome, and most likely all … Read more
How do I know if a variable is set in Bash? For example, how do I check if the user gave the first parameter to a function? function a { # if $1 is set ? } 3 37
What is the scope of variables in javascript? Do they have the same scope inside as opposed to outside a function? Or does it even matter? Also, where are the variables stored if they are defined globally? 2 27 TLDR JavaScript has lexical (also called static) scoping and closures. This means you can tell the … Read more
Which method of checking if a variable has been initialized is better/correct? (Assuming the variable could hold anything (string, int, object, function, etc.)) if (elem) { // or !elem or if (typeof elem !== ‘undefined’) { or if (elem != null) { 3 31
How do I determine if variable is undefined or null? My code is as follows: var EmpName = $(“div#esd-names div#name”).attr(‘class’); if(EmpName == ‘undefined’){ // DO SOMETHING }; <div id=”esd-names”> <div id=”name”></div> </div> But if I do this, the JavaScript interpreter halts execution. 3 33
This question’s answers are a community effort. Edit existing answers to improve this post. It is not currently accepting new answers or interactions. How would you explain JavaScript closures to someone with a knowledge of the concepts they consist of (for example functions, variables and the like), but does not understand closures themselves? I have … Read more
Java: “error: cannot find symbol”
You must understand the difference between a class and an instance of that class. If you see a car on the street, you know immediately that it’s a car even if you can’t see which model or type. This is because you compare what you see with the class “car”. The class contains which is similar to … Read more
If you’re on the main display, then or if you’re using csh or tcsh before running your app. Actually, I’m surprised it isn’t set automatically. Are you trying to start this application from a non-graphic terminal? If not, have you modified the default .profile, .login, .bashrc or .cshrc? Note that setting the DISPLAY to :0.0 … Read more
A local variable is defined within the scope of a block. It cannot be used outside of that block. Example: if(x > 10) { String local = “Local value”; } I cannot use local outside of that if block. An instance field, or field, is a variable that’s bound to the object itself. I can use it in the object without the need … Read more
