Fix incorrect Object/function checking in node index.js wrapper

[kudlav]

Node
Fix incorrect Object/function checking in node index.js wrapper.

Changes

• replace options instanceof Object by typeof options === "object"
• replace options.request instanceof Function by typeof options.request === "function"

Using instanceof Object can be problematic because it won't work correctly for all objects.
E.g. the following object { ratio: 1, request: [Function: request] } returns options instanceof Object false and at the same time typeof options.request === "function" true. Simillar to the function check.

Other changes

• Use modern let and const instead of var to prevent hoisting issues
• Unify single and double quote to double quote - use just one type in a single file
• do not repeat if (options... every time, use nested if

[louwers]

Looks good, the Node.js codebase can be modernized a bit. I would recommend setting up an automated formatter, maybe with pre-commit. Could you add some regression tests for the scenarios you describe?

Maybe we can create a Node.js channel on Slack to coordinate the continued development of the Node.js platform?