Select

(module
  (func (export "select_simple") (result i32)
    ;; load two values onto the stack
    i32.const 10
    i32.const 20
    ;; change to `1` (true) to get the first value (`10`)
    i32.const 0
    select
  )
  (func (export "select_externref") (param $value externref) (param $condition i32) (result externref)
    ;; this is "select t", the explicitly typed variant
    ref.null extern
    local.get $value
    local.get $condition
    select (result externref)
  )
)

const url = "{%wasm-url%}";
await WebAssembly.instantiateStreaming(fetch(url)).then((result) => {
  const { select_simple, select_externref } = result.instance.exports;
  console.log(select_simple());
  // Expected output: 20
  // If the second parameter is zero, returns the first parameter (which may be an arbitrary JS value)
  const map = new Map();
  console.log(select_externref(map, 0));
  // Expected output: [object Map]
  console.log(select_externref(map, -1));
  // Expected output: null
});

;; push two values onto the stack
i32.const 10
i32.const 20
;; change to `1` (true) to get the first value (`10`)
i32.const 0
select