br_table

(module ;; Import the browser console object, which you'll need to pass in from JavaScript (import "console" "log" (func $log (param i32))) (func ;; Label each block for easy reference ;; (they can also be referenced by their index) (block $outer_block (block $middle_block (block $inner_block ;; Choose which block to break out of based on their order in the br_table ;; 0 is `$inner_block`, 1 is `$outer_block`, 2 is `$middle_block` i32.const 0 ;; Create a br_table with three targets (br_table $inner_block $outer_block $middle_block) ;; The code will never reach this point since we broke out of the block unreachable ) ;; If you jump out of `$inner_block` but stay in `$middle_block`, ;; 42 will be logged ;; If you jump out of `$middle_block` also, ;; by jumping out of either `$middle_block` or `$outer_block`, ;; this will be skipped i32.const 42 call $log ) ) ) (start 1) ;; Run the first function automatically ) 

const url = "{%wasm-url%}"; await WebAssembly.instantiateStreaming(fetch(url), { console }); 

;; Add true to the top of the stack so that the `if` statement is executed. i32.const 1 (if ;; 2 (then (block ;; 1 (loop ;; 0 ;; Add a variable to the top of the stack i32.const 2 ;; 0 = jump to `block`; since item 0 in br_table is 1, it jumps up one level ;; 1 = jump to `if`; since item 1 in br_table is 2, it jumps up two levels ;; 2 = jump to `loop`; since item 2 in br_table is 0, it doesn't jump any levels (causing an infinite loop) ;; Create a br_table with the targets (br_table 1 2 0) ) ) ) )