block: Wasm text instruction
Theblock statement creates a label that can later be branched out of with abr.
Theloop statement is the opposite of theblock statement, in the sense that while branching to aloop jumps to the beginning of the loop, branching to ablock jumps to the end of the block; that is, out of the block.
Try it
(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 },);Syntax
wat
;; 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)| Instruction | Binary opcode |
|---|---|
block | 0x02 |