Currently, index is updated on every scroll event, even if its value has not changed. This makes it tricky to add a function that is run only when a new section comes into view (which is probably what is required in #11, for example).
To see the current behavior, add the following line to the end of the script block in App.svelte in the demo.
$: console.log('Current section: ' + index);
As you scroll, 'Current section: 0' is logged many times.
The new version in this pull request only updates index (and calls any corresponding functions) if a new section is scrolled into position. This is done by using a new variable i rather than index as the index variable for the for-loop. Thus, index is only changed when the current section has changed.
Rich-Harris
commented
3 years ago
Currently,
indexis updated on every scroll event, even if its value has not changed. This makes it tricky to add a function that is run only when a new section comes into view (which is probably what is required in #11, for example).To see the current behavior, add the following line to the end of the script block in
App.sveltein the demo.As you scroll, 'Current section: 0' is logged many times.
The new version in this pull request only updates
index(and calls any corresponding functions) if a new section is scrolled into position. This is done by using a new variableirather thanindexas the index variable for the for-loop. Thus,indexis only changed when the current section has changed.