nodejs
delete searchParams during iteration will cause skipping
Version
v22.13.1
Platform
Linux BeenoTung-Archlinux-laptop-kudu 6.14.9-arch1-1 #1 SMP PREEMPT_DYNAMIC Thu, 29 May 2025 21:42:15 +0000 x86_64 GNU/Linux
Subsystem
No response
What steps will reproduce the bug?
When running below code in nodejs
let url = new URL('http://example.com?a=1&b=2&c=3&d=4')
let { searchParams } = url
console.log('all keys:', Array.from(searchParams.keys()))
for (let key of searchParams.keys()) {
console.log('delete:', { key })
searchParams.delete(key)
}
console.log('remains keys:', Array.from(searchParams.keys()))
How often does it reproduce? Is there a required condition?
The behavior can be reproduced every time, without additional condition.
What is the expected behavior? Why is that the expected behavior?
The expected behavior is to delete all params.
Workaround is to collect all elements into an array then iterate on the array, instead of iterate on the iterator directly, which is not intuitive IMO.
What do you see instead?
The observed output is listed as below
all keys: [ 'a', 'b', 'c', 'd' ]
delete: { key: 'a' }
delete: { key: 'c' }
remains keys: [ 'b', 'd' ]
Only the odd index keys are deleted.
Additional information
No response
this will happen as you are deleting from array, so the array size is getting smaller but the iterator continues to increment. step 0: array:[a,b,c,d] ; i = 0 ; array[i] = a step 1: array: [b,c,d] (we deleted a ) ; i = 1; array[i] = c after deleting 'c' iterator i gets larger than the size of array so loop stops
It is actually the expected behavior.
.keys() is providing the iterator for the keys of the URLSearchParams.
When the internal state of the URLSearchParams changed, it should also be updated immediately.
It is also why you need to use Array.from when you do the console.log.
Because the provided value is not an array but iterator of internal state.
thanks for the clarification, then we've to wrap it with Array.from() if we plan to delete elements when iterating 👌