if...else

if 用來處理條件式。如果在記憶體堆疊中的最後一個值為 true (1)，就會執行陳述式裡的程式；如果為 false (0)，則執行其他陳述式。

嘗試一下

(module
  ;; import the browser console object, you'll need to pass this in from JavaScript
  (import "console" "log" (func $log (param i32)))

  (func
    i32.const 0 ;; change to positive number (true) if you want to run the if block
    (if
      (then
        i32.const 1
        call $log ;; should log '1'
      )
      (else
        i32.const 0
        call $log ;; should log '0'
      )
    )
  )

  (start 1) ;; run the first function automatically
)

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

語法

wasm

i32.const 0
(if
  (then
    ;; do something
  )
  (else
    ;; do something else
  )
)

指令	二進制運算碼
`if`	`0x04`
`else`	`0x05`