How can I loop over object keys in Xel scripts?

Question

I'm making a project with Xel, but I am stuck on a problem.

I want to loop through the keys of an object, and here's a minimal example of what I'm trying to get:

const strings = import("xel:strings")

let obj = {
    key1: "value",
    key2: "value2,"
    key3: "value3"
}

let i = 0
// This "keys" function is hypothetical. I'm not sure what I should do here.
// "keys" might return an array
const allKeys = keys(obj)
while ( len(allKeys) > i ) {
    const key = allKeys[i]
    const value = obj[key]
    print(strings.format("%v: %v", key, value))
    i = i + 1
}

But this doesn’t seem to work... How can I achieve this?

What programming language?

Peter Mortensen
– Peter Mortensen

2025-05-22 14:49:54 +00:00
Commented May 22 at 14:49 — Peter Mortensen
– Peter Mortensen, Commented May 22 at 14:49
@PeterMortensen Thanks for your interest, this is Xel

Jack G.
– Jack G.

2025-05-22 14:56:59 +00:00
Commented May 22 at 14:56 — Jack G.
– Jack G., Commented May 22 at 14:56

Nimantha · Accepted Answer · 2025-06-18 11:41:41Z

In Xel, iterating over the keys of an object is a common requirement, especially when working with dynamic data structures. While earlier versions lacked native support for this functionality, recent updates have addressed the gap.

Before Xel v0.13.0, looping over object keys in Xel was unfortunately not directly possible due to the lack of built-in object manipulation functions. However, I'm happy to announce that Xel v0.13.0 (released in 9th June 2025) introduces the xel:object module, which makes this task straightforward!

Here's how you can achieve your goal using the new features:

Solution


const object = import("xel:object")
const strings = import("xel:strings")

let obj = {
    key1: "value",
    key2: "value2",
    key3: "value3"
}

const allKeys = object.keys(obj) // returns an array of keys

let i = 0

while (len(allKeys) > i) {
    const key = allKeys[i]
    const value = object.get(obj, key) // or obj[key]

    print(strings.format("%v: %v", key, value))
    i = i + 1
}

Explanatuon:

object.keys(obj): This function from the xel:object module takes your object obj and returns an array containing all of its keys (property names).
object.get(obj, key): We now use object.get(obj, key) to retrieve the value associated with a given key.

Alternative Method:

You can also use the object.entries() function and a forEach loop for a more concise solution:


const object = import("xel:object")
const strings = import("xel:strings")
const array = import("xel:array")

let obj = {
    key1: "value",
    key2: "value2",
    key3: "value3"
}

const entries = object.entries(obj) // returns an array of [key, value] pair

array.forEach(entries, (entry) {
    const key = entry[0]
    const value = entry[1]

    print(strings.format("%v: %v", key, value))
})

This method uses object.entries() to get an array where each element is an array containing the key and value, then iterates over the entries using array.forEach() (introduced in earlier Xel releases).

Nimantha · Accepted Answer · 2025-06-18 11:43:07Z

0

const strings = import("xel:strings")

let obj = {
    key1: "value",
    key2: "value2",
    key3: "value3"
}

let keys = map.keys(obj)
let i = 0

while (i < len(keys)) {
    let key = keys[i]
    let value = obj[key]
    print(strings.format("%v: %v", key, value))
    i = i + 1
}


map.keys(obj) — retrieves an array of keys from the map-like object.

len(keys) — returns the number of keys.

obj[key] — accesses the value dynamically using the key string.

strings.format() — formats the string output.

Another method
As of current Xel (or XelScript) behavior, there is no map.keys() function built-in. Instead, to loop over keys of an object, Xel provides a native for loop syntax for objects.

strings = import("xel:strings")

obj = {
    key1: "value",
    key2: "value2",
    key3: "value3"
}

for (let key in obj) {
    let value = obj[key]
    print(strings.format("%v: %v", key, value))
}

edited Jun 18 at 11:43

Nimantha

6,5476 gold badges32 silver badges78 bronze badges

answered May 22 at 15:20

user607464

1086 bronze badges

2 Comments

Jack G. May 22 at 15:29

Thanks for your answer! But that does not resolve the issue. I am getting this error when I try that: Error: Runtime Error: Cannot resolve variable map

Jack G. May 22 at 15:42

Appreciate the edit! Sadly, I get: Error: Syntax Error: Expected Primary Expression, got 'Let' from L9C6 to L9C9.

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