Question

I am fairly new to NodeJS and to JavaScript in general. Here is my script:

var fs = require('fs') ;

var temp = "???";

var test = function (){
    fs.readdir("./", function(err,result){
    temp = result;            // i change the temp's value
    console.log("inter result ....."+temp);        //  temp's value changed
    setTimeout(pr,1000,"inter setTimeout: "+temp);  //  temp's value changed 
    });
}

var pr = function (str){
    console.log("Print str: "+ str);
} ;


test();

setTimeout(pr,1000,"Out setTimeout print: "+temp);  //  Why here temp's value not change???

How can I change to the var temp’s value outside the callback?

Answer 1

setTimeout(pr,1000,"Out setTimeout print: "+temp);

is the same as

var str = "Out setTimeout print: " + temp;
setTimeout(pr, 1000, str);

At this point of time temp still is "???". You have to use

setTimeout(function() {
  pr("Out setTimeout print: "+temp);
}, 1000);