Azure function complains of JS syntax error when syntax is valid

Question

I have an Azure function defined in JS

module.exports = async function (context, req) {
    if (req.query.name || (req.body && req.body.name)) {

        // generate mock result
        const mockChecker = new mockCheckBuild();
        const result = await mockChecker.runAsync();

        context.res = {
            body: result
        };
    }
    else {
        context.res = {
            status: 400,
            body: "Please pass a name on the query string or in the request body"
        };
    }
    context.done();
};

function mockCheckBuild() {
   this.statuses = ['Failed', 'Complete'];

   this.branchId = 808;

   this.buildNumbers = ['0.1.1.1023', '0.1.1.1024', '0.1.1.1025'];

   this.runAsync = async function() {
      return new Promise(resolve => 
        setTimeout(() =>
            resolve({
                branchId: this.branchId,
                latestBuild: this.statuses.randomElement(),
                buildStatus: this.buildNumbers.randomElement()
            })
        , 2000)
      );
   };

   return this;
}

Array.prototype.randomElement = function()
{
    const index = Math.floor(Math.random() * this.length);
    return this[index];
};

which I've run through numerous syntax validators that validate it is correct JavaScript. I will also note that the Azure syntax highlighter is highlighting words like async and const.

However, when I run it I get

"Exception while executing function: Functions.CheckLatestBuild -> One or more errors occurred. -> D:\home\site\wwwroot\CheckLatestBuild\index.js:1\n(function (exports, require, module, __filename, __dirname) { module.exports = async function (context, req) {\n
^^^^^^^^\n\nSyntaxError: Unexpected token function\n at createScript (vm.js:56:10)\n at Object.runInThisContext (vm.js:97:10)\n at Module._

Any idea why? Or any advice on how to better investigate?

Answer 1

Azure Functions v1 runs Node 6.x, which doesn't support async. If you instead try Functions v2 Preview, you can run Node 8.x (and soon 10.x), and async will work.