What is a flag variable?

Question

Recently I came across flag variables, but I have no idea what they do.

I am little unsure about when to use a flag variable and how to go about it.

I Googled it but there weren't any specific examples related to my context (of JavaScript).

Desmonddesmoulins

Asked and answered here: https://mcmap.net/q/262795/-enum-flags-in-javascript – Carioca

my first hit in google javascriptkit.com/javatutors/valid2.shtml – Tepid

look at that example,its pretty confusing!!! – Desmonddesmoulins

Answer 1

Flag Variables Defined and Uses says:

A flag variable, in its simplest form, is a variable you define to have one value until some condition is true, in which case you change the variable's value. It is a variable you can use to control the flow of a function or statement, allowing you to check for certain conditions while your function progresses.

As an example:

// errors is the flag variable
var errors = 0;

for(var i = 0; i < 10; i++) {
  if(i == 6) {  // Your error condition
    errors++;
  }
}

if(errors) {  // Is the flag "up"? (i.e. > 0)
  alert("There was a problem!");
}

Stace

Answer 2

A flag is a variable used to have some value until some condition becomes true,then we change it to false and print the output (Initially flag considered as true)

Beating

In that case it would start out as false and switch to true, not the other way around. – Ammadis

Answer 3

Flag variables are the same for all languages, whether it's RUBY, Python, Javascript or C++.

A flag variable is usually given one value, 0 or 1, True or False. It's used as a Boolean variable where the result toggles between 0 (False) and 1 (True) or as used by the programmer. Some prefer flag = 0 and change it to flag = 1 in the program to perform an action.

Kowtko

Answer 4

A flag variable, it is a variable you define to have one value until some condition is true or false in which case you change the variable's value. It is a variable you can use to control the flow of a function or statement, allowing you to check for certain conditions while your function executing.

Flag variable is same in every language

Flag variable is boolean variable.

Sarmentose

Answer 5

its a simple example of how it works

hi document.getElementById("myflag").addEventListener("click", changetext);

let flag = true;
function changetext() {
  if (flag) {
    document.getElementById("myflag").innerHTML = "bye";
    flag = !flag;
  } else {
    document.getElementById("myflag").innerHTML = "hi";
    flag = !flag;
  }
}

Cloison