How to convert a javascript for loop to while loop

Question

I have the following code

let branch_timings=locations.branch_timings;
for(let key of Object.keys(branch_timings)){
  branch_timings[key].timingsEnabled=false;
}

console.log(locations);

I tried converting this to while loop like this:

let keys=locations.keys()
let i=0;
while(i<keys.length)
{
    let key=keys[i];
    branch_timings[key].timingsEnabled=false;
    i++;
}

console.log(locations);

when I run my while loop code this is the error I get

TypeError: locations.keys is not a function

This is part of a bigger code from a question i posted earlier. Every solution I have found is in either for loop or forEach I am trying to learn how to convert these loops to while. I am fairly new to javascript, your opinions will be appreciated.

`let keys = Object.keys(branch_timings)` – Unmitigated Aug 20 '20 at 14:27 — Unmitigated, Aug 20 '20 at 14:27

score 1 · Answer 1 · answered Aug 20 '20 at 14:28

1

You need Object.keys to enumerate keys.

let keys=Object.keys(locations);
let i=0;
while(i<keys.length)
{
    let key=keys[i];
    branch_timings[key].timingsEnabled=false;
    i++;
}

console.log(locations);

answered Aug 20 '20 at 14:28

TheMisir

4,083
1
27
37

To expand on why this is correct vs. the OP's example, the answer lies in the fact that [`Object.keys()` is not a prototype method](https://stackoverflow.com/questions/57017736/why-is-object-keys-method-not-added-to-object-prototype). – esqew Aug 20 '20 at 14:29

score 0 · Answer 2 · answered Aug 20 '20 at 14:33

0

Correct translation should be that.

let keys= Object.keys(locations.branch_timings);
let i=0;
while(i < keys.length)
{
    let key=keys[i];
    locations.branch_timings[key].timingsEnabled=false;
    i++;
}

answered Aug 20 '20 at 14:33

Eclipse

3
2

thankyou so much, this worked! could you please explain to me why do we write Object.keys instead of locations.keys – SystematicallyWrongHa Aug 20 '20 at 14:37
@esqew explained that in his comment, keys() method is not part of object prototype, you have to use it from Object wrapper – Eclipse Aug 20 '20 at 14:49

score 0 · Answer 3 · answered Aug 20 '20 at 14:35

0

To use locations.keys() Make Sure your variable location is of type Array. The TypeError you're getting suggests the variable location is not an Array.

If it's an object, you should use Object.keys(locations).

answered Aug 20 '20 at 14:35

Nick Thakkar

862
1
9
13

How to convert a javascript for loop to while loop

3 Answers3