does nodejs settimeout share variable in different loops

Question

While test the settimeout function of Nodejs, Put settimeout in two for loops ,if both the for loops have the same variables name i, It seems to be that the two settimeout functions are sharing the variable.

code:

for (var i = 1; i <= 3; i++) { 
    var tm1=setTimeout(function(){
         console.log(i); 
            }, 0); 
}
for (var i = 1; i <= 4; i++) {
    (function (x) {
        var tm2=setTimeout(function () { console.log(x); }, 100);
    })(i);
}

Result: 6 6 6 1 2 3 4 5
If the for loops have different variables name n and i, the results look all right

code:

for (var n = 1; n <= 3; n++) { 
    //change the variable name from i to n
    setTimeout(function(){
         console.log(n); 
            }, 0); 
}
for (var i = 1; i <= 5; i++) {
    (function (x) {
        var tm2=setTimeout(function () { console.log(x); }, 100);
    })(i);
}

Result: 4 4 4 1 2 3 4 5

How to understand this?

Possible duplicate of [How do JavaScript closures work?](http://stackoverflow.com/questions/111102/how-do-javascript-closures-work) — Jeremy J Starcher, Apr 18 '16 at 10:08

score 1 · Accepted Answer · answered Apr 18 '16 at 08:21

1

There is only function scope and no block scope in ES5. Your observation has nothing to do with the setTimeout function but with the javascript variable scope

read here

answered Apr 18 '16 at 08:21

jahnestacado

593
3
9

does nodejs settimeout share variable in different loops

1 Answers1