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).
In programming, a flag is a predefined bit or bit sequence that holds a binary value. Typically, a program uses a flag to remember something or to leave a sign for another program.
flags defines a distributed command line system, replacing systems like getopt() , optparse , and manual argument processing. Rather than an application having to define all flags in or near main() , each Python module defines flags that are useful to it.
Data flags are commonly used to signify either bad data or missing data in a dataset. In MATLAB the official flag value is NaN (not a number). More typically a number larger than any possible value of the variables in the dataset is used such as 1.0e32, or 99999.
A Flag is a boolean variable that signals when some condition exists in a program. When a flag is set to true, it means some condition exists When a flag is set to false, it means some condition does not exist. if(score > 95) highscore = true; Here, highscore is a flag indicating that the score is above 95.
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!");
}
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