The "let" binding
let binding lets you set custom binding context properties that you can then reference in the bindings of all descendant elements.
Here is a basic example of setting values using
let that are then available in all descendant elements, regardless of context changes.
If the expression you supply unwraps any observable values, the expression will be re-evaluated whenever any of those observables change. Additionally, the bindings for all descendant elements will be re-evaluated as well.
Note 1: Using “let” without a container element
Just like other control flow bindings, you can use
let without any container element to host it. See the documentation for
foreach for more details.
Note 2: Performance considerations when using “let”
If the expression you provide to the
let binding unwraps any observables, each descendant binding will include an additional dependency on the
let binding. This is true whether or not the binding references any of the custom context properties. If you want to make an observable value available through
let, it is generally better to set the observable itself rather than unwrap it and set the value.
None, other than the core Knockout library.