examples/change_string.html

<html>
<body>

<script src="../wail.js"></script>
<!-- wabt.js used for compiling WAT to WASM -->
<script src="https://cdn.jsdelivr.net/gh/AssemblyScript/wabt.js/index.js"></script>
<script>

WabtModule().then(function(wabt) {

const logString = function(offset) {
    const bytes = new Uint8Array(memory.buffer, offset);

    const stringBytes = [];

    for (i = 0; bytes[i] !== 0x00; i++) {
        stringBytes.push(bytes[i]);
    }

    const stringArray = new Uint8Array(stringBytes);

    const string = new TextDecoder('utf8').decode(stringArray);

    console.log(string);
}

const wasmText = `
(module
  (import "env" "log" (func $log (param i32)))
  (import "env" "mem" (memory 1))
  (data (i32.const 0) "Old Text")
  (func (export "printMsg")
    i32.const 0
    call $log))
`;

const wat = wabt.parseWat('change_string.wast', wasmText);
const binary = wat.toBinary({});

const memory = new WebAssembly.Memory({initial:1});

const importObject = {
    env: {
        log: logString,
        mem: memory
    },
};

const wail = new WailParser(binary.buffer);

wail.editDataEntry(0, {
    data: "New, longer text"
});

wail.parse();

WebAssembly.instantiate(wail.write(), importObject).then(function(wasm) {
    wasm.instance.exports.printMsg();
});

});
</script>

</body>
</html>