Why isn't this javascript while loop running in node?

Question

I'm trying to make it so the program repeatedly accepts input and repeats it back until "exit" is inputted. Right now the loop doesn't run, and I don't know why since the exit variable is set to false. Here's my code:

var read = require("read");
var exit = false;


function OutsideLoop (exit) {

while(exit === false){

        read({prompt: "> "}, function (err, result) {

        console.log("");
        console.log(result);
        console.log("Type in more input or type 'exit' to close the program.");

        if(result === "exit"){
            exit = true;};
        });


};

};


OutsideLoop();

Thanks for the help guys. I have a similar loop working using if/then instead of while, so I rewrote this one along the same lines.

You could say if(!exit)exit = false; in your OutsideLoop function at the very top of your code. Then you won't need to pass the parameter. — StackSlave
– StackSlave, Commented Nov 7, 2013 at 22:59
Since there's only one condition to exit the loop, simpler to do while (exit !== true) {do stuff}. — RobG
– RobG, Commented Nov 7, 2013 at 23:02
Looks like I have to teach you something again @minitech. when @Ber calls OutsideLoop() with no argument it is undefined, therefore my comment is correct. — StackSlave
– StackSlave, Commented Nov 7, 2013 at 23:02

Pointy · Accepted Answer · 2013-11-07 22:54:40Z

5

You've declared "exit" as a parameter to the function, so the outer declaration has no effect on the logic inside the function. You don't pass anything to the function when you call it, so "exit" is undefined and the === test fails.

If you either pass "exit" to the function, or else take out the parameter from the function declaration, it'll work — maybe. That "read" function is asynchronous, so I'm not sure how node will behave.

answered Nov 7, 2013 at 22:54

Pointy

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Ry- · Accepted Answer · 2013-11-07 22:58:56Z

1

Pointy’s right about the parameter shadowing the outer variable you’ve declared. However, what you’ll end up with is a horrible busy loop. Node.js is event-based; use its events properly.

function promptUser() {
    read({prompt: "> "}, function(err, result) {
        console.log();
        console.log(result);
        console.log("Type in more input or type 'exit' to close the program.");

        if(result !== "exit") {
            promptUser();
        }
    });
}

promptUser();

answered Nov 7, 2013 at 22:58

Ry-♦

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willy · Accepted Answer · 2013-11-07 22:57:09Z

0

You aren't passing exit when you call the function. It should be:

    OutsideLoop( exit );

On the last line.

answered Nov 7, 2013 at 22:57

willy

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