loop_scope_broken.js

#! /usr/bin/env node

var foo = function() {
    for (i=0; i<=2; i++) {
        console.log("foo i: %d", i)
    }
}

var main = function() {
    for (i=0; i<=2; i++) {
        console.log("main i1: %d", i)
        foo();
        console.log("main i2: %d", i)
    }
}

main()

loop_scope_error.js

#! /usr/bin/env node

"use strict"

var foo = function() {
    for (i=0; i<=2; i++) {
        console.log("foo i: %d", i)
    }
}

var main = function() {
    for (i=0; i<=2; i++) {
        console.log("main i1: %d", i)
        foo();
        console.log("main i2: %d", i)
    }
}

main()

loop_scope_fixed.js

#! /usr/bin/env node

"use strict"

var foo = function() {
    var i = 0;
    for (i; i<=2; i++) {
        console.log("foo i: %d", i)
    }
}

var main = function() {
    var i = 0;
    for (i; i<=2; i++) {
        console.log("main i1: %d", i)
        foo();
        console.log("main i2: %d", i)
    }
}

main()

outputs.md

Broken

$ ./loop_scope_broken.js
main i1: 0
foo i: 0
foo i: 1
foo i: 2
main i2: 3

Error

$ ./loop_scope_error.js
/Users/skhandkar/tmp/loop_scope_error.js:12
    for (i=0; i<=2; i++) {
          ^

ReferenceError: i is not defined
    at main (/Users/skhandkar/tmp/loop_scope_error.js:12:11)
    at Object.<anonymous> (/Users/skhandkar/tmp/loop_scope_error.js:19:1)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Function.Module.runMain (module.js:441:10)
    at startup (node.js:139:18)
    at node.js:968:3

Fixed

$ ./loop_scope_fixed.js
main i1: 0
foo i: 0
foo i: 1
foo i: 2
main i2: 0
main i1: 1
foo i: 0
foo i: 1
foo i: 2
main i2: 1
main i1: 2
foo i: 0
foo i: 1
foo i: 2
main i2: 2