What is the best way to utilize the `Headers` iterator within a web browser?

Question

What is the best way to utilize the `Headers` iterator within a web browser?

Currently, I am attempting to utilize the Headers iterator as per the guidelines outlined in the Iterator documentation.

  let done = false
  while ( ! done ) {
    let result = headers.entries()
    if ( result.value ) {
      console.log(`yaay`)
    } 
    if ( result.done ) {
      console.log(`finished`)
      done = true
    } 
  }

Upon execution of this code snippet, I encounter a TypeScript error:

Property 'value' does not exist on type 'IterableIterator<[string, string]>'.

Despite referencing the specification, which indicates that the property value should be present in any Iterator and that the method headers.entries() yields an Iterator.

Is there a way to extract the values from a Headers object?

javascript typescript dom ecmascript-6 iterator

Answer 1

Answer №1

As per the specifications, the value property is expected to be present on every Iterator

No, it is actually found on the iterator result object that is returned by the Iterator's .next() method. To access it, you would write:

const iter = headers.entries();
let { value, done } = iter.next();
while (!done) {
    console.log('hooray', value);
    ({ value, done } = iter.next());
}
console.log('done');

But it is recommended not to manually implement the iteration protocol. Simply use for … of instead:

for (const value of headers.entries()) {
    console.log('hooray', value);
}
console.log('done');

Answer 2

As per the specifications, the value property is expected to be present on every Iterator

No, it is actually found on the iterator result object that is returned by the Iterator's .next() method. To access it, you would write:

const iter = headers.entries();
let { value, done } = iter.next();
while (!done) {
    console.log('hooray', value);
    ({ value, done } = iter.next());
}
console.log('done');

But it is recommended not to manually implement the iteration protocol. Simply use for … of instead:

for (const value of headers.entries()) {
    console.log('hooray', value);
}
console.log('done');

Answer 3

Answer №2

If you need to work with headers, one approach is to utilize Array.from(headers) along with traditional map/forEach methods for manipulation.

const headers= new Headers({some: 'thing'})

Array.from(headers).forEach(([key,val])=>{console.log(key,val)})

Answer 4

If you need to work with headers, one approach is to utilize Array.from(headers) along with traditional map/forEach methods for manipulation.

const headers= new Headers({some: 'thing'})

Array.from(headers).forEach(([key,val])=>{console.log(key,val)})

What is the best way to utilize the `Headers` iterator within a web browser?

Answer №1

Answer №2

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