Transpiling es7 to es6 error unexpected identifier

Question

I have transpiled a javascript code from es7 to es6 since I need to use

Node.js 6.9.5

but I keep getting this error when transpiling:

Unexpected Identifier keyValues[key] = yield DbStorage.get(key);

my code looks like this:

getMany: function (keys) {
    return new Promise((resolve, reject) => {
        let keyValues = {};

        for(let key of keys){
            keyValues[key] = await DbStorage.get(key);
        }

        resolve(keyValues);
    });
},

and the transpiled code looks like this:

 getMany: function (keys) {
    return new Promise((resolve, reject) => {
        let keyValues = {};
        for (let key of keys) {
            keyValues[key] = yield DbStorage.get(key);
        }
        resolve(keyValues);
    });
},

I am using typescript to transpile my tsconfig.json looks like this:

{
"allowJs" : true,
"compilerOptions": {
    "target": "es6",
    "sourceMap": true,
    "removeComments": false,
    "listFiles" : false,
    "diagnostics" : false, 
    "outDir" : "build",
    "allowJs" : true,
    "inlineSourceMap" : false
},
"include" : ["collaboration/*"],
"exclude": [ "build", "node_modules" ]

}

so what's wrong with this ?

Answer 1

You're using await in a non-async function, which is incorrect. getMany should be async, which amongst other things means you don't need new Promise:

getMany: async function (keys) {
//       ^^^^^
    let keyValues = {};

    for (let key of keys){
        keyValues[key] = await DbStorage.get(key);
    }

    return keyValues;
},

It's very strange of the TypeScript compiler to turn that erroneous await into an erroneous yield, but it could be an edge-case bug in the TypeScript compiler. If you fix the usage, hopefully it will transpile correctly.