block

(module
  ;; import the browser console object, you'll need to pass this in from JavaScript
  (import "console" "log" (func $log (param i32)))
  ;; create a function that takes in a number as a param,
  ;; and logs that number if it's not equal to 100.
  (func (export "log_if_not_100") (param $num i32)
    (block $my_block
      ;; $num is equal to 100
      local.get $num
      i32.const 100
      i32.eq
      (if
        (then
          ;; branch to the end of the block
          br $my_block
        )
      )
      ;; not reachable when $num is 100
      local.get $num
      call $log
    )
  )
)

const url = "{%wasm-url%}";
await WebAssembly.instantiateStreaming(fetch(url), { console }).then(
  (result) => {
    const log_if_not_100 = result.instance.exports.log_if_not_100;
    log_if_not_100(99);
    // Expected output: 99
    log_if_not_100(100);
    // Should not log anything
    log_if_not_100(101);
    // Expected output: 101
  },
);

;; label the block so that it can be branched to.
(block $my_block
  ;; branch to the block.
  ;; most of the time you'll want to put this in an if statement and only branch on condition,
  ;; otherwise the following control flow are unreachable.
  br $my_block
  ;; this will never be reached, since the br jumped out of the block already.
  unreachable
)