How to use the assemblyscript.CompilerTarget function in assemblyscript

function compile(source) {
    var module = assemblyscript_1.Compiler.compileString(source, {
        target: assemblyscript_1.CompilerTarget.WASM32,
        memoryModel: assemblyscript_1.CompilerMemoryModel.MALLOC,
        silent: true
    });
    var wasmFile;
    if (!module) {
        throw Error('compilation failed');
    }
    module.optimize();
    if (!module.validate()) {
        throw Error('validation failed');
    }
    wasmFile = module.emitBinary();
    module.dispose();
    return new Buffer(wasmFile);
}
/**